feat: Add Users

[SMadani]

Adds support for Users endpoints.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 97.60%. Comparing base (005f1f6) to head (29bcb68).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/main/kotlin/com/vonage/client/kt/Users.kt	94.73%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main       #9      +/-   ##
============================================
- Coverage     97.74%   97.60%   -0.15%     
- Complexity      120      128       +8     
============================================
  Files            15       16       +1     
  Lines           355      375      +20     
  Branches         25       28       +3     
============================================
+ Hits            347      366      +19     
- Partials          8        9       +1     

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