Support of OIDC Implicit Flow

Current Situation

OIDC Identity Services support the Authentication Code Flow. In this flow the "client secret" is transferred to the OIDC Identity Provider

Desired Behavior

OIDC Identity Services should support the Implicit Flow. In this flow the "client secret" is not transferred to the OIDC Identity Provider. The Implicit Flow will be used when the settings of the OIDC Identity Service do not provide the "client secret".