Deprecate webhook endpoints

[joe94]

Once Scytale starts owning XMiDT's webhook registry, suggested steps to deprecate the webhook endpoints include:

Phase 1

Have a flag for Tr1d1um to either (1) serve the request or (2) simply redirecting it to Scytale.

Handling request: In this mode, Tr1d1um will create a new request (must pay close attention to capability check configurations between Scytale and Tr1d1um) to Scytale and then return the response to the caller. Callers should notice no difference from the current behavior in this mode.
Redirection: Perform an HTTP redirect to the scytale endpoint. This would require Tr1d1um users to setup their services and credentials to follow redirects and ultimately update the endpoint they use for webhooks

Phase 2

Drop support for the flag and only support redirection.

Phase 3

Drop support of endpoints.