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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• I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
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[codecov-commenter]

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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 43.67%. Comparing base (3954224) to head (8d9ce4b).

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   43.71%   43.67%   -0.04%     
==========================================
  Files         111      116       +5     
  Lines        6693     6772      +79     
==========================================
+ Hits         2926     2958      +32     
- Misses       3532     3576      +44     
- Partials      235      238       +3     

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[cloudxxx8]

LGTM