Add and document option to use StartTLS with mail_room.

config/mail_room.yml.example

@@ -6,6 +6,8 @@
     # :port: 993
     # # Whether the IMAP server uses SSL
     # :ssl: true
+    # # Whether the IMAP server uses StartTLS
+    # :start_tls: false
     # # Email account username. Usually the full email address.
     # :email: "replies@gitlab.example.com"
     # # Email account password

doc/incoming_email/README.md

@@ -88,6 +88,8 @@ In this example, we'll use the Gmail address `gitlab-incoming@gmail.com`.
         :port: 993
         # Whether the IMAP server uses SSL
         :ssl: true
+        # Whether the IMAP server uses StartTLS
+        :start_tls: false
         # Email account username. Usually the full email address.
         :email: "gitlab-incoming@gmail.com"
         # Email account password
@@ -161,6 +163,8 @@ In this example, we'll use the Gmail address `gitlab-incoming@gmail.com`.
         :port: 993
         # Whether the IMAP server uses SSL
         :ssl: true
+        # Whether the IMAP server uses StartTLS
+        :start_tls: false
         # Email account username. Usually the full email address.
         :email: "gitlab-incoming@gmail.com"
         # Email account password