Redmine

This patch adds IMAP email retrieval via OAuth2.

1. Register an application in Azure and grant "IMAP.AccessAsUser.All" permission. Note the tenant ID, client ID and client secret.
2. Initialize the OAuth token:
   

   rake redmine:email:o365_oauth2_init token_file=config/email_oauth2 client=YOUR_CLIENT_ID secret=YOUR_CLIENT_SECRET tenant=YOUR_TENANT_ID

3. Fetch messages using the token:
   

   rake redmine:email:receive_imap_oauth2 token_file=config/email_oauth2 host=outlook.office365.com port=993 ssl=1 username=YOUR_ACCOUNT

Duplicate of: #40325, #37688, #37705, #37705