Count a ready mark only from a listed account, after the last push and the label (issue 722)

Review of #303: anyone who can comment could turn a stale label into a mark,
and a long thread hid the newest comment. The forge now reads the pull
request's whole timeline and takes a "ready at" comment only from the
accounts in the trusted setting ready-authors (default the mesh's own forge
account and the operator's), written after the label was last added and after
the last push; any other author is ignored and said in the log.

modules/gitea/module.json

@@ -109,6 +109,13 @@
       }
     }
   },
+  "settings": {
+    "ready-authors": {
+      "kind": "preference",
+      "default": "mesh-admin jschoubben",
+      "why": "the forge accounts whose comment \"ready at <full head sha>\" marks a pull request ready for mesh-delivery to merge, separated by spaces: the mesh's own forge account and the operator's (novox/hq issue 722). A comment by any other account is ignored and said in the forge's log. Trusted: who may have a change merged is the operator's word"
+    }
+  },
   "resources": [
     {
       "id": "mesh-state",
@@ -122,6 +129,14 @@
       "path": "${dir:mesh-state}/state",
       "mode": "0700"
     },
+    {
+      "id": "ready-authors",
+      "type": "file",
+      "path": "${dir:mesh-state}/ready-authors",
+      "mode": "0600",
+      "trusted": true,
+      "content": "# The accounts whose \"ready at <sha>\" comment marks a pull request ready (novox/hq issue 722), from the setting\n# ready-authors, written by the mesh. Replaced on every push; change the setting, never this file.\nauthors=${setting:ready-authors}\n"
+    },
     {
       "id": "state",
       "type": "directory",
@@ -246,7 +261,8 @@
           "MESH_GITEA_ADMIN_USER": "mesh-admin",
           "MESH_GITEA_ADMIN_PASSWORD_FILE": "${dir:state}/admin.secret",
           "MESH_GITEA_STATE_DIR": "${dir:runtime-state}",
-          "MESH_RECEIVES": "${dir:grants}/npm.json"
+          "MESH_RECEIVES": "${dir:grants}/npm.json",
+          "MESH_GITEA_READY_AUTHORS_FILE": "${dir:mesh-state}/ready-authors"
         }
       },
       {