client_ids are required to be ULIDs

docs/config.schema.json

@@ -387,7 +387,7 @@
       "properties": {
         "client_id": {
           "description": "The client ID",
-          "type": "string"
+          "$ref": "#/definitions/ULID"
         },
         "redirect_uris": {
           "description": "List of allowed redirect URIs",
@@ -1732,6 +1732,13 @@
           ]
         }
       ]
+    },
+    "ULID": {
+      "description": "A ULID as per https://github.com/ulid/spec",
+      "type": "string",
+      "pattern": "^[0123456789ABCDEFGHJKMNPQRSTVWXYZ]{26}$",
+      "minLength": 26,
+      "maxLength": 26
     }
   }
 }