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/dhcpcd/module.json

@@ -1,6 +1,9 @@
 {
   "module": "dhcpcd",
   "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",
@@ -25,7 +34,7 @@
       "mode": "0644",
       "into": "block",
       "at": "start",
-      "content": "# The mesh's two lines (module dhcpcd, novox/hq ADR 0117). Global options, so\n# kept above any interface line; read at dhcpcd's next start.\nnohook resolv.conf\ndenyinterfaces mesh0\n"
+      "content": "# The mesh's two lines (module dhcpcd, novox/hq ADR 0117, ADR 0223): the\n# resolver file is this module's, written whole beside this file. Global\n# options, so kept above any interface line; read at dhcpcd's next start.\nnohook resolv.conf\ndenyinterfaces mesh0\n"
     }
   ]
 }