feat: feature flag http dest example

[vinayteki95]

What are the changes introduced in this PR?

1. webhook destination is enhanced to read content-type header and generate response body in the appropriate format (xml, urlencoded, json)
2. This feature is enabled based on feature flag dest_transformer_webhook_form_support. New feature flag sdk is used to achieve this.

This is only a draft and will be updated to use better naming convention for feature flag and better imports for cdk/v2/webhook.

What is the related Linear task?

Resolves INT-2991

Please explain the objectives of your changes below

To experiment with the new feature flag sdk and perform end-to-end testing.

Any changes to existing capabilities/behaviour, mention the reason & what are the changes ?

webhook destination now respects content-type headers

Any new dependencies introduced with this change?

feature-flag-sdk

Any new generic utility introduced or modified. Please explain the changes.

N/A

Any technical or performance related pointers to consider with the change?

How efficient is feature-flag-sdk?

@coderabbitai review

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Developer checklist

• My code follows the style guidelines of this project

• No breaking changes are being introduced.

• All related docs linked with the PR?

• All changes manually tested?

• Any documentation changes needed with this change?

• Is the PR limited to 10 file changes?

• Is the PR limited to one linear task?

• Are relevant unit and component test-cases added in new readability format?

Reviewer checklist

• Is the type of change in the PR title appropriate as per the changes?

• Verified that there are no credentials or confidential data exposed with the changes.

[krishna2020]

Suggested change

	return { payload, contentTypeSimplified };
	return { getFORMPayload(payload), contentTypeSimplified };

[vinayteki95]

We don't have to convert this into FORMPayload ourselves as rudder-server takes care of it.
Follow this link to see what rudder-server is doing: https://github.com/rudderlabs/rudder-server/blob/f22e8f4bb61893af132f3f4386155c83c695fd51/router/network.go#L124

But I see the issue here, we need to flatten the json for rudder-server to properly convert it into form-values

I think a simple flattening will do the job here @krishna2020

[krishna2020]

test case can be made readable by restricting only to necessary fields in the payload

[sonarcloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)
C Reliability Rating on New Code (required ≥ A)
2 New Major Issues (required ≤ 1)

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