Add config support for using Microsoft Graph with MailRoom

This commit only changes the configuration template file in preparation
for upgrading MailRoom to support the Microsoft Graph API with OAuth2
instead of IMAP.

References:

1. https://gitlab.com/gitlab-org/gitlab/-/issues/214900
2. https://github.com/tpitale/mail_room/pull/125

changelogs/unreleased/sh-update-mailroom-config.yml

+---
+title: Add config support for using Microsoft Graph with MailRoom
+merge_request: 58250
+author:
+type: added

config/gitlab.yml.example

@@ -210,6 +210,13 @@ production: &base
     # Whether to expunge (permanently remove) messages from the mailbox when they are deleted after delivery
     expunge_deleted: false
 
+    # For Microsoft Graph support
+    # inbox_method: microsoft_graph
+    # inbox_options:
+    #   tenant_id: "YOUR-TENANT-ID"
+    #   client_id: "YOUR-CLIENT-ID"
+    #   client_secret: "YOUR-CLIENT-SECRET"
+
   ## Consolidated object store config
   ## This will only take effect if the object_store sections are not defined
   ## within the types (e.g. artifacts, lfs, etc.).

config/mail_room.yml

@@ -19,6 +19,13 @@
       :delete_after_delivery: true
       :expunge_deleted: <%= config[:expunge_deleted].to_json %>
 
+      <% if config[:inbox_method] %>
+      :inbox_method: <%= config[:inbox_method] %>
+      <% end %>
+      <% if config[:inbox_options].is_a?(Hash) %>
+      <%= config.slice(:inbox_options).to_yaml(indentation: 8).gsub(/^---\n/, '') %>
+      <% end %>
+
       :delivery_method: sidekiq
       :delivery_options:
         :redis_url: <%= config[:redis_url].to_json %>

spec/config/mail_room_spec.rb

@@ -16,7 +16,9 @@ RSpec.describe 'mail_room.yml' do
     }
     cmd = "puts ERB.new(File.read(#{absolute_path(mailroom_config_path).inspect})).result"
 
-    output, status = Gitlab::Popen.popen(%W(ruby -rerb -e #{cmd}), absolute_path('config'), vars)
+    result = Gitlab::Popen.popen_with_detail(%W(ruby -rerb -e #{cmd}), absolute_path('config'), vars)
+    output = result.stdout
+    status = result.status
     raise "Error interpreting #{mailroom_config_path}: #{output}" unless status == 0
 
     YAML.load(output)
@@ -68,6 +70,39 @@ RSpec.describe 'mail_room.yml' do
     end
   end
 
+  context 'when both incoming email and service desk email are enabled for Microsoft Graph' do
+    let(:gitlab_config_path) { 'spec/fixtures/config/mail_room_enabled_ms_graph.yml' }
+    let(:queues_config_path) { 'spec/fixtures/config/redis_queues_new_format_host.yml' }
+    let(:gitlab_redis_queues) { Gitlab::Redis::Queues.new(Rails.env) }
+
+    it 'contains the intended configuration' do
+      expected_mailbox = {
+        email: 'gitlab-incoming@gmail.com',
+        name: 'inbox',
+        idle_timeout: 60,
+        expunge_deleted: true
+      }
+      expected_options = {
+        redis_url: gitlab_redis_queues.url,
+        sentinels: gitlab_redis_queues.sentinels
+      }
+      expected_inbox_options = {
+        tenant_id: '12345',
+        client_id: 'MY-CLIENT-ID',
+        client_secret: 'MY-CLIENT-SECRET',
+        poll_interval: 60
+      }
+
+      expect(configuration[:mailboxes].length).to eq(2)
+      expect(configuration[:mailboxes]).to all(include(expected_mailbox))
+      expect(configuration[:mailboxes].map { |m| m[:inbox_method] }).to all(eq('microsoft_graph'))
+      expect(configuration[:mailboxes].map { |m| m[:inbox_options] }).to all(eq(expected_inbox_options))
+      expect(configuration[:mailboxes].map { |m| m[:delivery_options] }).to all(include(expected_options))
+      expect(configuration[:mailboxes].map { |m| m[:delivery_options] }).to all(include(expected_options))
+      expect(configuration[:mailboxes].map { |m| m[:arbitration_options] }).to all(include(expected_options))
+    end
+  end
+
   def clear_queues_raw_config
     Gitlab::Redis::Queues.remove_instance_variable(:@_raw_config)
   rescue NameError

spec/fixtures/config/mail_room_enabled_ms_graph.yml

+test:
+  incoming_email:
+    enabled: true
+    address: "gitlab-incoming+%{key}@gmail.com"
+    user: "gitlab-incoming@gmail.com"
+    mailbox: "inbox"
+    expunge_deleted: true
+    inbox_method: "microsoft_graph"
+    inbox_options:
+      tenant_id: "12345"
+      client_id: "MY-CLIENT-ID"
+      client_secret: "MY-CLIENT-SECRET"
+      poll_interval: 60
+
+  service_desk_email:
+    enabled: true
+    address: "gitlab-incoming+%{key}@gmail.com"
+    user: "gitlab-incoming@gmail.com"
+    mailbox: "inbox"
+    expunge_deleted: true
+    inbox_method: "microsoft_graph"
+    inbox_options:
+      tenant_id: "12345"
+      client_id: "MY-CLIENT-ID"
+      client_secret: "MY-CLIENT-SECRET"
+      poll_interval: 60