cloudflare-dns: config from settings, not static manifest env (ADR 0051)

Which zone, domain and ingress are a mesh's facts, not the module's — so they
are settings merged into a config file the mesh manages, read by fromEnv, rather
than the empty env placeholders I wrongly baked in. The token stays the one
own-secret. The module now describes a Cloudflare registrar; which zone is a
setting, so the same description serves every mesh. Typechecks; manifest parses.

modules/cloudflare-dns/client.ts

@@ -23,14 +23,19 @@ export class CloudflareClient {
   ) {}
 
   static fromEnv(env: NodeJS.ProcessEnv = process.env): CloudflareClient {
+    // Which zone, domain and ingress are a mesh's own facts, not this module's — so they are
+    // settings, merged into a config file the mesh manages (novox/hq ADR 0051), read here. The
+    // token is the one secret and stays an own-secret. Env is honoured as a fallback for a
+    // hand-run instance, but the deployed path is the config file settings fill.
+    const config = readConfig(env.MESH_CLOUDFLARE_CONFIG_FILE);
     const token = env.MESH_CLOUDFLARE_TOKEN ?? readSecret(env.MESH_CLOUDFLARE_TOKEN_FILE);
-    const zoneId = env.MESH_CLOUDFLARE_ZONE_ID;
-    const domain = env.MESH_PUBLIC_DOMAIN;
-    const ingress = env.MESH_PUBLIC_INGRESS;
+    const zoneId = config.zone ?? env.MESH_CLOUDFLARE_ZONE_ID;
+    const domain = config.domain ?? env.MESH_PUBLIC_DOMAIN;
+    const ingress = config.ingress ?? env.MESH_PUBLIC_INGRESS;
     if (!token || !zoneId || !domain || !ingress) {
       throw new Error(
-        "cloudflare-dns needs MESH_CLOUDFLARE_TOKEN (or _FILE), MESH_CLOUDFLARE_ZONE_ID, " +
-          "MESH_PUBLIC_DOMAIN and MESH_PUBLIC_INGRESS — it cannot register a name without them",
+        "cloudflare-dns is not configured — set its zone, domain and ingress in settings (and the " +
+          "token as its own-secret); until then it registers nothing",
       );
     }
     return new CloudflareClient(token, zoneId, domain, ingress);
@@ -103,3 +108,20 @@ function readSecret(path: string | undefined): string | undefined {
     return undefined;
   }
 }
+
+interface Config {
+  zone?: string;
+  domain?: string;
+  ingress?: string;
+}
+
+/** The settings-managed config file (a JSON document the mesh merges settings into). Absent or
+ *  unparseable yields an empty config, which fromEnv then reports as unconfigured. */
+function readConfig(path: string | undefined): Config {
+  if (!path) return {};
+  try {
+    return JSON.parse(readFileSync(path, "utf8")) as Config;
+  } catch {
+    return {};
+  }
+}

modules/cloudflare-dns/module.json

@@ -37,6 +37,14 @@
       "path": "/var/lib/cloudflare-dns/grants",
       "mode": "0700"
     },
+    {
+      "id": "config",
+      "type": "file",
+      "path": "/var/lib/cloudflare-dns/config.json",
+      "merge": "json",
+      "content": "{}",
+      "mode": "0600"
+    },
     {
       "id": "provisioner",
       "type": "container",
@@ -47,11 +55,10 @@
         "GRANTS": "/grants",
         "MESH_CLOUDFLARE_TOKEN_FILE": "/run/secrets/token",
         "MESH_BROKER_FILE": "/run/secrets/broker",
-        "MESH_CLOUDFLARE_ZONE_ID": "",
-        "MESH_PUBLIC_DOMAIN": "",
-        "MESH_PUBLIC_INGRESS": ""
+        "MESH_CLOUDFLARE_CONFIG_FILE": "/run/config/config.json"
       },
       "volumes": [
+        "/var/lib/cloudflare-dns/config.json:/run/config/config.json:ro",
         "/var/lib/cloudflare-dns/grants:/grants",
         "/var/lib/cloudflare-dns/token:/run/secrets/token:ro",
         "/var/lib/cloudflare-dns/broker:/run/secrets/broker:ro"