Improve user feedback when using manual onboarding

[BohoCode]

Story

As a TPP registering an application via manual onboarding I want to get feedback when my application fails to register so that I don't have to submit support tickets to the ASPSP that owns the sandbox.

Acceptance criteria

• When doing an incorrect registration (e.g. with an invalid SSA signed with RS256, or with an invalid redirect URL (e.g. google.com rather than https://google.com) a reasonable error string is presented to the TPP allowing them to correct their registration attempt.

Tasks

Release Notes

Affected App: X

Description: X