feat: add validation library to be compatible with ingestion svc [PIPE-1834]

[BonapartePC]

Description

add validation library to be compatible with ingestion svc

Linear Ticket

https://linear.app/rudderstack/issue/PIPE-1834/gateway-validation-library

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 74.82%. Comparing base (78fb917) to head (400b824).
Report is 13 commits behind head on master.

Files with missing lines	Patch %	Lines
gateway/validation/validation.go	68.42%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5408      +/-   ##
==========================================
+ Coverage   74.76%   74.82%   +0.05%     
==========================================
  Files         438      441       +3     
  Lines       61339    61453     +114     
==========================================
+ Hits        45862    45984     +122     
+ Misses      12935    12929       -6     
+ Partials     2542     2540       -2     

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[ktgowtham]

@mihir20 @fracasula , closing this PR as discussed.