chore: default webhook contract version to v2

[vinayteki95]

Description

As part of complete migration to webhook v2 contract, we are defaulting to v2 when features service is not ready yet.

Linear Ticket

Resolves INT-2757
https://linear.app/rudderstack/issue/INT-2757/stage-3-or-clean-up-or-no-more-adapters-to-convert-v2-v1-spec

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

All modified and coverable lines are covered by tests ✅

Project coverage is 76.89%. Comparing base (a38b4f5) to head (7371767).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5659      +/-   ##
==========================================
- Coverage   77.04%   76.89%   -0.15%     
==========================================
  Files         483      483              
  Lines       65534    65534              
==========================================
- Hits        50491    50393      -98     
- Misses      12295    12376      +81     
- Partials     2748     2765      +17     

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[Copilot]

Pull Request Overview

This PR updates the webhook contract defaults as part of the migration to webhook v2 by enabling the upgraded source transform flag.

• In testhelper/transformertest/builder.go, the JSON payload is updated to include "upgradedToSourceTransformV2": true.
• In services/transformer/features.go, the default feature configuration for v2 is applied.
• In services/transformer/features_impl_test.go and regulation-worker/cmd/main_test.go, the tests are updated to reflect the new default source transformer version.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
testhelper/transformertest/builder.go	Updated JSON features payload to include v2 flag
services/transformer/features_impl_test.go	Modified test expectations to use v2 as the default version
services/transformer/features.go	Changed default JSON configuration to set upgradedToSourceTransformV2 true
regulation-worker/cmd/main_test.go	Updated test fixture to include the new v2 feature flag

Comments suppressed due to low confidence (2)

testhelper/transformertest/builder.go:137

• Ensure that the new feature flag 'upgradedToSourceTransformV2' added in this test helper is complemented by tests that verify the expected behavior in production code.

features := []byte(`{"routerTransform": {}, "supportSourceTransformV1": true, "upgradedToSourceTransformV2": true}`)

services/transformer/features_impl_test.go:108

• [nitpick] Consider adding additional test cases to verify the behavior when only one of the source transform flags is set, to ensure that all edge cases are clearly handled.

It("If source transform is not v1 or v2, it should panic as v0 is deprecated", func() {

[mihir20]

LGTM