Remove square brackets from display names before using in mention

[acelaya]

Depends on #6908

Closes #6891

Remove any appearance of [ and ] from display-name mentions, since those characters are reserved to delimit the display name itself.

This is something that is rare to occur, and in most cases dropping those characters should not cause any confusion.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.43%. Comparing base (61173a4) to head (f486c1b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6912   +/-   ##
=======================================
  Coverage   99.43%   99.43%           
=======================================
  Files         273      273           
  Lines       10574    10576    +2     
  Branches     2545     2545           
=======================================
+ Hits        10514    10516    +2     
  Misses         60       60           

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[robertknight]

Slack thread with info on the 16 LMS users who had used square brackets in their display name. Uses include:

• Organizational affiliation
• Pronouns
• Aliases