luci-config: fine-grained acls

appengine/config_service/proto/service_config.proto

 // Copyright 2015 The Swarming Authors. All rights reserved.
 // Use of this source code is governed by the Apache v2.0 license that can be
 // found in the LICENSE file.
 
 // Schemas for config files in services/luci-config config set.
 //
 // In this file, "string pattern" is an exact string (can't have a colon) or a
 // string that starts with "regex:", followed by a regular expression. In case
 // of regex, the pattern must match an entire string, as if it was sorrounded by
 // ^ and $.
@@ skipping 34 matching lines @@
 message ProjectsCfg {
   // All projects served by this instance of Luci.
   repeated Project projects = 1;
 }
 
 // Schema of acl.cfg file.
 message AclCfg {
   // Name of the group that has access to all services/* config sets.
   optional string service_access_group = 1;
   // Name of the group that has access to all projects/* config sets.
+  // Only trusted services should be in this group.
   optional string project_access_group = 2;
 }
 
 // Schema for import.cfg. It specified how to import configuration files from
 // external sources.
 message ImportCfg {
 
   message Gitiles {
     // Request timeout in seconds when requesting commit log.
     optional int32 fetch_log_deadline = 1;
@@ skipping 80 matching lines @@
   message Message {
     // Textual representation of the message.
     optional string text = 1;
     // If an error, a config is considered invalid. Defaults to INFO.
     optional Severity severity = 2;
   }
   // Errors, warnings and other information found during validation.
   // If at least one error is found, the config is considered invalid.
   repeated Message messages = 1;
 }