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/postgres/module.json

@@ -59,6 +59,33 @@
     "superuser": "${dir:state}/superuser.secret",
     "reader": "${dir:state}/reader.secret"
   },
+  "data": {
+    "own": [
+      {
+        "id": "store",
+        "path": "${dir:store-data}",
+        "class": "valuable",
+        "backup": {
+          "dump": "docker exec -u postgres postgres sh -c 'cd /var/lib/postgresql/data/dumps && for db in $(psql -Atc \"select datname from pg_database where oid >= 16384 order by 1\"); do pg_dump -Fc -f \"$db.dump.partial\" \"$db\" && mv \"$db.dump.partial\" \"$db.dump\" || exit 1; done'",
+          "into": "dumps"
+        },
+        "why": "every consumer's database; copied by the dump below, since a running store's files are not a consistent copy"
+      },
+      {
+        "id": "dumps",
+        "path": "${dir:dumps}",
+        "class": "rebuildable",
+        "why": "last night's dump of the store, made again every night"
+      }
+    ],
+    "consumers": {
+      "postgres-database": {
+        "class": "valuable",
+        "in": "store",
+        "why": "a consumer's rows are the only copy of what it wrote"
+      }
+    }
+  },
   "resources": [
     {
       "id": "state",
@@ -128,12 +155,5 @@
         }
       }
     ]
-  },
-  "contributions": [
-    {
-      "seat": "node-backup",
-      "kind": "backup",
-      "content": "run docker exec -u postgres postgres sh -c 'cd /var/lib/postgresql/data/dumps && for db in $(psql -Atc \"select datname from pg_database where oid >= 16384 order by 1\"); do pg_dump -Fc -f \"$db.dump.partial\" \"$db\" && mv \"$db.dump.partial\" \"$db.dump\" || exit 1; done'\npath ${dir:dumps}\n"
-    }
-  ]
+  }
 }