MessageRedirectsController has conceptional but partial duplication

[danielmarbach]

Describe the suggested improvement

MessageRedirectsController has the possibility to create new redirects or updating existing redirects. Creating new redirects involves validation of the input data and handling of more elaborate conflict handling with potentially existing or dependent redirects.

Updating redirects doesn't provide the same validation. It checks for existing redirects but uses different reason phrases but doesn't check for dependents.

Additionally, MessageRedirectRequest contains RetryExisting which is never used by ServicePulse. This flag on the input data model is never checked on the update redirects call.

It might be worthwhile cleaning up the controller and the input model.

Additional Context

No response