Fixed user mentions

[rimi-itk]

Link to ticket

#2380

Description

Fixes user mentions by

1. Patching tinymce-mention (see below for details)
2. Adding and using a simple query filter on /api/users?projectUsersAccess=current

Details on how to fix the "query" issue in tinymce-mention:

• No longer works on tinymce 6.7 StevenDevooght/tinyMCE-mention#93 (comment)
• Autocomplete Rendring Issue in Firefox StevenDevooght/tinyMCE-mention#1 (comment)

Screenshot of the result

Before:

After:

Checklist

• My code passes all test cases.
• My code passes our static analysis suite.
• My code passes our continuous integration process.

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