Issue 6383 - introduce switchable app_id

templates/manifest.json.tmpl

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 {
   "manifest_version": 2,
   {%- if releaseBuild %}
   "name": "__MSG_name__",
   {%- else %}
   "name": "__MSG_name_devbuild__",
@@ skipping 15 matching lines @@
 
   {%- if metadata.has_section('compat') and metadata.has_option('compat', 'edge') %}
   "minimum_edge_version": {{metadata.get('compat', 'edge')|json}},
   {%- endif %}
 
   {%- if type == 'gecko' %}
   "applications":
   {
     "gecko":
     {
-      "id": {{metadata.get('general', 'id')|json}}
+      "id": {{app_id|json}}
 
       {%- if metadata.has_section('compat') and metadata.has_option('compat', 'gecko') %}
       ,
       "strict_min_version": {{metadata.get('compat', 'gecko')|json}}
       {%- endif %}
 
       {%- set updateURLSetting = 'updateURL' if releaseBuild else 'devbuildUpdateURL' %}
       {%- if metadata.has_option('general', updateURLSetting) %}
       ,
       "update_url": {{metadata.get('general', updateURLSetting)|json}}
@@ skipping 69 matching lines @@
     "managed_schema": {{metadata.get('general', 'managedStorageSchema')|json}}
   },
   {%- endif %}
 
   {%- if metadata.has_option('general', 'contentSecurityPolicy') %}
   "content_security_policy": {{metadata.get('general', 'contentSecurityPolicy')|json}},
   {%- endif %}
 
   "_dummy": false
 }