Declare every module's data; the backup holder measures it (hq ADR 0233)

Backup lines are derived from each module's data section instead of written by hand; the holder
measures declared items, reads the array under them, and deletes a retired item only after a last
restore point; the Go providers say each held consumer's size so an empty replacement is seen.

modules/mongodb/module.json

@@ -45,6 +45,33 @@
   "own-secrets": {
     "root": "${dir:state}/root.secret"
   },
+  "data": {
+    "own": [
+      {
+        "id": "data",
+        "path": "${dir:data}",
+        "class": "valuable",
+        "backup": {
+          "dump": "docker exec mongodb-server sh -c 'printf \"password: %s\\n\" \"$(cat /run/secrets/root)\" > /tmp/.backup.yaml && mongodump --quiet --config /tmp/.backup.yaml --username root --authenticationDatabase admin --archive; s=$?; rm -f /tmp/.backup.yaml; exit $s' > ${dir:dumps}/all.archive.partial && mv ${dir:dumps}/all.archive.partial ${dir:dumps}/all.archive",
+          "into": "dumps"
+        },
+        "why": "every consumer's database; copied by the dump, not as live files"
+      },
+      {
+        "id": "dumps",
+        "path": "${dir:dumps}",
+        "class": "rebuildable",
+        "why": "last night's dump, made again every night"
+      }
+    ],
+    "consumers": {
+      "mongodb-database": {
+        "class": "valuable",
+        "in": "data",
+        "why": "a consumer's documents are the only copy of what it wrote; a consumer that keeps something irreplaceable here says so (kept-by)"
+      }
+    }
+  },
   "resources": [
     {
       "id": "state",
@@ -122,12 +149,5 @@
         }
       }
     ]
-  },
-  "contributions": [
-    {
-      "seat": "node-backup",
-      "kind": "backup",
-      "content": "run docker exec mongodb-server sh -c 'printf \"password: %s\\n\" \"$(cat /run/secrets/root)\" > /tmp/.backup.yaml && mongodump --quiet --config /tmp/.backup.yaml --username root --authenticationDatabase admin --archive; s=$?; rm -f /tmp/.backup.yaml; exit $s' > ${dir:dumps}/all.archive.partial && mv ${dir:dumps}/all.archive.partial ${dir:dumps}/all.archive\npath ${dir:dumps}\n"
-    }
-  ]
+  }
 }