feat: webhook v2 spec upgrade

[vinayteki95]

Description

• V2 adapter is introduced to send v2 spec events
• Source transformer payloads will be built differently for different specs (v1 and v2)
• Features service will be aware of v2 flag from transformer and pick adapter accordingly

Linear Ticket

Resolves INT-2802

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 91.30435% with 6 lines in your changes missing coverage. Please review.

Project coverage is 73.30%. Comparing base (7aa1895) to head (633bb3c).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
services/transformer/features_impl.go	25.00%	2 Missing and 1 partial ⚠️
services/transformer/features.go	0.00%	2 Missing ⚠️
gateway/webhook/webhook.go	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5224      +/-   ##
==========================================
- Coverage   73.30%   73.30%   -0.01%     
==========================================
  Files         423      423              
  Lines       59908    59950      +42     
==========================================
+ Hits        43917    43946      +29     
- Misses      13534    13541       +7     
- Partials     2457     2463       +6     

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