i3status-rust: name the pacman-contrib package apart from the update script, and expect it in the test (issue 628)

The package took the id `updates`, which the update script already holds, so the node-engine refused two resources with one identity.

modules/docker-compose/README.md

@@ -19,8 +19,9 @@ runtime is missing or unreachable rather than an empty list.
 
 - **An owner for a package both workstations already carry.** On both, `docker-compose` 5.5.0 is
   installed explicitly by hand, as the plugin in `/usr/lib/docker/cli-plugins`. Assigning the module
-  changes nothing on disk; from then on the package is the mesh's, upgraded with the machine and
-  given back when the module goes.
+  changes nothing on disk; from then on the mesh says the package is needed, and it is upgraded with
+  the machine. Unassigning the module leaves the package installed: the node-engine never removes a
+  package a declaration stopped naming (novox/hq ADR 0303).
 - **The projects become visible from the mesh** without a shell on the machine: which are running,
   where their files are, their containers, logs and rendered configuration.
 - **No account-level copy of the plugin** exists on either workstation (`~/.docker/cli-plugins` is

modules/i3status-rust/README.md

@@ -2,7 +2,7 @@
 
 The bars as a module (novox/hq ADR 0208, research 026/05).
 
-- Installs `i3status-rust`. The update block's `checkupdates` comes from `pacman-contrib`, which the `pacman` module installs on every node; two modules declaring one package is refused at composition.
+- Installs `i3status-rust`, and `pacman-contrib` for the update block's `checkupdates`. The `pacman` module declares `pacman-contrib` too; several modules may declare one package (novox/hq ADR 0303), so each declares what it needs.
   Claims the mesh's `node-bar` seat (no verbs yet, ADR 0208 §2) and renders the blocks other modules
   contribute to it (ADR 0255, below). Requires `x11-display` on its own
   machine: its bars are i3bar's.

modules/i3status-rust/cmd/i3status-rust-tools/manifest_test.go

@@ -23,7 +23,8 @@ func TestItClaimsTheBarSeatAndRequiresTheXDisplay(t *testing.T) {
 	if !reflect.DeepEqual(m.Requires, []string{"x11-display"}) {
 		t.Fatalf("requires: %v", m.Requires)
 	}
-	if present, absent := m.packages(); !reflect.DeepEqual(present, []string{"i3status-rust"}) || absent != nil {
+	// pacman-contrib for the update block's checkupdates, declared here though the pacman module declares it too (ADR 0303).
+	if present, absent := m.packages(); !reflect.DeepEqual(present, []string{"i3status-rust", "pacman-contrib"}) || absent != nil {
 		t.Fatalf("packages: %v, absent %v", present, absent)
 	}
 }

modules/i3status-rust/module.json

@@ -35,6 +35,11 @@
       "type": "package",
       "package": "i3status-rust"
     },
+    {
+      "id": "checkupdates",
+      "type": "package",
+      "package": "pacman-contrib"
+    },
     {
       "id": "configuration-dir",
       "type": "directory",