Give /etc/resolv.conf to the uplink's holder (hq ADR 0223)

The program that manages a machine's network is the one that would rewrite
the resolver file, so its module now writes it: networkmanager,
systemd-networkd and dhcpcd render the same template from the resolver's
holders. resolv-conf declares nothing for one release, so every machine
hands the file over in one apply; it is removed once unassigned everywhere.

modules/networkmanager/module.json

@@ -1,6 +1,9 @@
 {
   "module": "networkmanager",
   "version": "1",
+  "requires": [
+    "wildcard-resolution"
+  ],
   "capabilities": [
     "package-manager",
     "service-manager",
@@ -12,6 +15,12 @@
       "scope": "node"
     }
   ],
+  "facts": {
+    "resolvers": {
+      "path": "/etc/resolv.conf",
+      "template": "# Managed by the mesh, and written by the module holding this machine's uplink:\n# the program that manages the machine's network would otherwise rewrite this\n# file on every change of network, so its holder is the one that writes it\n# (novox/hq ADR 0117, ADR 0223). Replaced on every push; edit nothing here.\n#\n# Every resolver of the mesh, by address, and nothing else (novox/hq ADR 0223) \u2014\n# this machine's own first when it holds one, then the others by name. Each\n# answers the mesh's names from the same roster and forwards every other name, so\n# whichever answers first gives the one answer. There is no public resolver here:\n# a C library that asks every listed server at once and takes the first reply \u2014\n# musl, so every Alpine container \u2014 took a public resolver's \"no such name\" for\n# a mesh name and failed. A machine that reaches none of these has no names until\n# it does. Containers copy these lines from their machine.\n{{range index .Holders \"mesh-dns-resolver\"}}nameserver {{.Address}}\n{{end}}options timeout:1 attempts:2 edns0\n"
+    }
+  },
   "resources": [
     {
       "id": "package",
@@ -23,7 +32,7 @@
       "type": "file",
       "path": "/etc/NetworkManager/conf.d/50-mesh.conf",
       "mode": "0644",
-      "content": "# Managed by the mesh (module networkmanager). Replaced on every push; edit the\n# catalogue instead.\n#\n# This machine's uplink is NetworkManager's, and this file is the whole of what\n# the mesh asks of it (novox/hq ADR 0117): leave the resolver file to the mesh,\n# and leave the private network's interface alone. Nothing more. The mesh never\n# declares a connection profile, an address, a route, a wireless network or its\n# credentials \u2014 those are joined at the machine, by the person using it, and\n# the link they make is the only channel the mesh reaches this machine over. A\n# push that got a link wrong could not be undone by the next one.\n#\n# A drop-in of the mesh's own, beside NetworkManager.conf and whatever else the\n# operator keeps in this directory. NetworkManager reads the files here sorted by\n# name and a later one wins a key it sets again \u2014 so a file of the operator's\n# that sorts after this one (any name starting with a letter does) and sets dns=\n# or unmanaged-devices= overrides it. That is the operator's to decide, and the\n# reason this file sets nothing but the two keys it must.\n#\n# NetworkManager itself is the machine's: the mesh never starts, stops, enables\n# or disables it (its service is declared with no state), because stopping it\n# takes every link down, this machine's channel to the mesh included \u2014 and a\n# module unassigned by mistake must not be able to do that. When this file\n# changes, a running NetworkManager is reloaded (its D-Bus Reload call, which\n# re-reads its configuration \u2014 NetworkManager(8)), never restarted.\n\n[main]\n# The resolver file is the mesh's: resolv-conf writes /etc/resolv.conf and names\n# the mesh's resolver. Without this line NetworkManager rewrites that file on\n# every connectivity change \u2014 every network joined, every lease renewed \u2014\n# and the mesh's resolver is silently replaced while every surface of the mesh\n# still reads green. none: \"NetworkManager will not modify resolv.conf. This\n# implies rc-manager unmanaged\" (NetworkManager.conf(5), 1.58). On an adopted\n# machine the predecessor wrote the same line in a file of its own; both say one\n# thing, and the predecessor's is retired by hand after the take.\ndns=none\n\n[keyfile]\n# mesh0 is the private network's interface: the mesh brings it up and the mesh\n# alone configures it. A manager that considers every interface its own could\n# try to configure it, or tear it down on a profile change.\n#\n# unmanaged-devices rather than a [device-mesh0] section with managed=0, because\n# NetworkManager.conf(5) says a device unmanaged by this key \"is strictly\n# unmanaged and cannot be overruled by using the API like nmcli device set\n# $IFNAME managed yes\", while device*.managed \"can be overruled at runtime via\n# D-Bus\". The same page adds that device*.managed \"may be a better choice\" for\n# exactly those reasons \u2014 for an interface the operator might want to hand back\n# at runtime. For the mesh's own interface, strict is the point.\n#\n# += rather than =: the same page documents appending to a list-valued key set\n# earlier (\"plugins+=another-plugin\") as an extension of its key file format,\n# and unmanaged-devices is a device list. = would replace whatever devices the\n# operator already keeps NetworkManager away from; += adds this one to them\n# (novox/hq ADR 0102: a list is added to, never replaced). A file of the\n# operator's read after this one that sets the key with = replaces it again;\n# that is the operator's to decide.\nunmanaged-devices+=interface-name:mesh0\n"
+      "content": "# Managed by the mesh (module networkmanager). Replaced on every push; edit the\n# catalogue instead.\n#\n# This machine's uplink is NetworkManager's, and this file is the whole of what\n# the mesh asks of it (novox/hq ADR 0117): leave the resolver file to the mesh,\n# and leave the private network's interface alone. Nothing more. The mesh never\n# declares a connection profile, an address, a route, a wireless network or its\n# credentials \u2014 those are joined at the machine, by the person using it, and\n# the link they make is the only channel the mesh reaches this machine over. A\n# push that got a link wrong could not be undone by the next one.\n#\n# A drop-in of the mesh's own, beside NetworkManager.conf and whatever else the\n# operator keeps in this directory. NetworkManager reads the files here sorted by\n# name and a later one wins a key it sets again \u2014 so a file of the operator's\n# that sorts after this one (any name starting with a letter does) and sets dns=\n# or unmanaged-devices= overrides it. That is the operator's to decide, and the\n# reason this file sets nothing but the two keys it must.\n#\n# NetworkManager itself is the machine's: the mesh never starts, stops, enables\n# or disables it (its service is declared with no state), because stopping it\n# takes every link down, this machine's channel to the mesh included \u2014 and a\n# module unassigned by mistake must not be able to do that. When this file\n# changes, a running NetworkManager is reloaded (its D-Bus Reload call, which\n# re-reads its configuration \u2014 NetworkManager(8)), never restarted.\n\n[main]\n# The resolver file is the mesh's: this module writes /etc/resolv.conf itself,\n# listing the mesh's resolvers (novox/hq ADR 0223). Without this line\n# NetworkManager rewrites that file on\n# every connectivity change \u2014 every network joined, every lease renewed \u2014\n# and the mesh's resolver is silently replaced while every surface of the mesh\n# still reads green. none: \"NetworkManager will not modify resolv.conf. This\n# implies rc-manager unmanaged\" (NetworkManager.conf(5), 1.58). On an adopted\n# machine the predecessor wrote the same line in a file of its own; both say one\n# thing, and the predecessor's is retired by hand after the take.\n#\n# Not NetworkManager's own global DNS ([global-dns-domain-*] with rc-manager=file):\n# it writes its own header and composes the options line itself, so it cannot\n# write the mesh's file byte for byte, and the three uplink modules would write\n# three different files for one fact. dns=none, and the file declared beside it.\ndns=none\n\n[keyfile]\n# mesh0 is the private network's interface: the mesh brings it up and the mesh\n# alone configures it. A manager that considers every interface its own could\n# try to configure it, or tear it down on a profile change.\n#\n# unmanaged-devices rather than a [device-mesh0] section with managed=0, because\n# NetworkManager.conf(5) says a device unmanaged by this key \"is strictly\n# unmanaged and cannot be overruled by using the API like nmcli device set\n# $IFNAME managed yes\", while device*.managed \"can be overruled at runtime via\n# D-Bus\". The same page adds that device*.managed \"may be a better choice\" for\n# exactly those reasons \u2014 for an interface the operator might want to hand back\n# at runtime. For the mesh's own interface, strict is the point.\n#\n# += rather than =: the same page documents appending to a list-valued key set\n# earlier (\"plugins+=another-plugin\") as an extension of its key file format,\n# and unmanaged-devices is a device list. = would replace whatever devices the\n# operator already keeps NetworkManager away from; += adds this one to them\n# (novox/hq ADR 0102: a list is added to, never replaced). A file of the\n# operator's read after this one that sets the key with = replaces it again;\n# that is the operator's to decide.\nunmanaged-devices+=interface-name:mesh0\n"
     },
     {
       "id": "service",