OAuth2 authentication for email accounts

Some providers are switching their e-mail accounts from "classic" to "modern" authentication. This means primarily the switch from username and password to OAuth2 tokens.

This change affects, among other things, email retrieval and sending for Microsoft Office 365 and various Google products (GMail/GSuite).

This extension enables the use of OAuth2 tokens for authentication in ((OTRS)) Community Edition. Supported are (incl. SSL support):

• IMAP
• POP3
• SMTP

The already existing authentication by username and password can be used without any changes.

This extension allows initial manual login/confirmation via a web dialog of the service provider (e.g. Google) to obtain OAuth2 tokens from within OTRS. After this step, expired tokens will be automatically refreshed by OTRS.

Manual configuration of other providers besides Microsoft and Google is possible.

Relevant links:
https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-and-exchange-online-april-2020-update/ba-p/1275508
https://gsuiteupdates.googleblog.com/2020/03/less-secure-app-turn-off-suspended.html
https://developers.google.com/identity/protocols/OAuth2