feat: webhook v2 spec

[vinayteki95]

Description

Rudder-server webhook is upgraded to communicate with transformer via a new contract (v2 spec) while also deprecating v1, v0 specs.

• Server will panic if transformer is an older version with no support of v2 spec.
• Server will find out if the transformer version is not compatible by looking for upgradedToSourceTransformV2 flag in transformer features.

Corresponding documentation

NOTE: This is a breaking change which expects transformer to support v2 version. Do not merge until transformer is released with v2 support.

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.