Add Users Client

[SecondeJK]

This PR adds the ability to CRUD users with a new Users client.

Description

These endpoints have been moved from the Conversations API, into the Application API. It seems most logical to move them under their own Client namespace.

How Has This Been Tested?

Tests have been created for this new client.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[codecov-commenter]

Codecov Report

Merging #420 (1549c39) into main (b88a1fe) will increase coverage by 0.17%. The diff coverage is 84.67%.

@@             Coverage Diff              @@
##               main     #420      +/-   ##
============================================
+ Coverage     78.71%   78.89%   +0.17%     
- Complexity     2248     2304      +56     
============================================
  Files           214      218       +4     
  Lines          6071     6207     +136     
============================================
+ Hits           4779     4897     +118     
- Misses         1292     1310      +18     

Files Changed	Coverage Δ
src/Users/ClientFactory.php	0.00% <0.00%> (ø)
src/Users/Filter/UserFilter.php	73.07% <73.07%> (ø)
src/Users/Client.php	81.48% <81.48%> (ø)
src/Client.php	22.22% <100.00%> (+0.36%)	:arrow_up:
src/Entity/IterableAPICollection.php	77.24% <100.00%> (+2.24%)	:arrow_up:
src/Users/User.php	100.00% <100.00%> (ø)

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[SecondeJK]

Comments done