feat: Add model/DTOs and HTTP client for security-proxy-auth

[lindseysimple]

Closes #963. Add model/DTOs and HTTP client for security-proxy-auth.

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Codecov Report

Attention: Patch coverage is 40.50633% with 47 lines in your changes missing coverage. Please review.

Project coverage is 43.26%. Comparing base (80a711a) to head (4567c6a).

Files with missing lines	Patch %	Lines
clients/interfaces/mocks/AuthClient.go	0.00%	41 Missing ⚠️
clients/http/auth.go	75.00%	2 Missing and 2 partials ⚠️
dtos/requests/keydata.go	84.61%	1 Missing and 1 partial ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #964      +/-   ##
==========================================
- Coverage   43.29%   43.26%   -0.04%     
==========================================
  Files         112      117       +5     
  Lines        6860     6939      +79     
==========================================
+ Hits         2970     3002      +32     
- Misses       3646     3690      +44     
- Partials      244      247       +3     

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