OIDC authorization code flow error response

[AxelNennker]

Problem description
CAMARA-Security-Interoperability.md states that if the openid scope is missing then a 400 BAD request should be returned.
A HTTP response of 400 must not be used.

Expected behavior
Errors should be returned as specified in the OIDC standard.
That is, if the redirect_url is valid, then the error is conveyed through the redirect_url as defined in 3.1.2.6. Authentication Error Response