Add possibility to disable or restrict users mentions in RichText

[RomainLvr]

Checklist before requesting a review

Please delete options that are not relevant.

• I have read the CONTRIBUTING document.
• I have performed a self-review of my code.
• I have added tests that prove my fix is effective or that my feature works.
• This change requires a documentation update.

Description

• It fixes !35409
• Here is a brief description of what this PR does

This PR adds the ability to disable or restrict user mentions in RichText of different forms of response in Ticket/Changes/Problems

New option have been added to the Assistance section of profiles:

Dropdown with 3 values :

• Disabled (Mentions desactivées)
• Full (Mentions enabled with user list complete)
• Restricted (Mentions enabled with user list restricted to ticket actors)

Screenshots (if appropriate):

[Rom1-B]

As it also depends on whether the notification is activated, I think you should take the opportunity to add a tooltip (+ a check?).