Mention contacts in message body

[hamza221]

Is your feature request related to a problem? Please describe.

As a user, I want to be able to mention contacts directly in the message body or in a reply and I want to be able to identify the messages I got mentioned in easily

Describe the solution you'd like

• [x] In message body mention contacts can be mentioned with @ symbol
• [x] The contact gets added automatically to the "To" field
• [x] Mentions are rendered adequately in message envelope and preview text
• [x] mailbox can be filtered/sorted for messages that mention you

Competitor Analysis

• Gmail inserts an anchorTag with a mailto href once clicked it opens a new message composer to the address
• Outlook does the same but you can hover for quick actions and contact information (only for messages sent from outlook)

Work Package

• [x] #10110
• [x] #10111
• [x] #10112
• [ ] https://github.com/nextcloud/documentation/issues/12170

Describe alternatives you've considered

No response

Additional context

No response