static OidcIssuerService echoing(final String issuer) {
        return registeredService -> issuer;
    }
Immutable issuer service that always returns a static issuer.

@param issuer the issuer
@return the oidc issuer service
support/cas-server-support-oidc-core-api/src/main/java/org/apereo/cas/oidc/issuer/OidcIssuerService.java