Invalidate branch delete event on Bitbucket Data Center

[zakisk]

Issue

When a branch is deleted via the repository UI, a repo:refs_changed event is triggered, which is treated as a push event by PAC. As a result, PAC attempts to validate the commit information, leading to an error message. We should prevent this from occurring by ignoring such events directly within the ParsePayload function to avoid unnecessary log noise.

Solution

The payload of a repo:refs_changed event includes a changes array with fromHash and toHash fields. When a branch is deleted, the toHash field will contain a zero hash value (0000000000000000000000000000000000000000). Therefore, we should check the toHash value in the event payload, and if it matches the zero SHA, we should return early from the ParsePayload function without further processing.

[PuneetPunamiya]

@zakisk can you assign me this issue ?