feat: add user in pending group when requests to join an org

[4nt0ineB]

What

• This feature is enabled for validated org
• The user is added to the 'pending' group of an org when he requests to join it.
• The org admin can accept or reject.
• If an other org is requested by the user while waiting for approval, he is removed from the previous one.

Screenshot

Related issue(s) and discussion

• Fixes Create a new "pending" group of organization members #8781

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 5.88235% with 16 lines in your changes missing coverage. Please review.

Project coverage is 49.27%. Comparing base (dc04d18) to head (a0a3535).
Report is 465 commits behind head on main.

Files	Patch %	Lines
lib/ProductOpener/Orgs.pm	0.00%	11 Missing ⚠️
lib/ProductOpener/Users.pm	16.66%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10500      +/-   ##
==========================================
- Coverage   49.54%   49.27%   -0.28%     
==========================================
  Files          67       76       +9     
  Lines       20650    21863    +1213     
  Branches     4980     5235     +255     
==========================================
+ Hits        10231    10772     +541     
- Misses       9131     9769     +638     
- Partials     1288     1322      +34     

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[stephanegigandet]

Thank you!