@PostMapping(value = WEBAUTHN_ENDPOINT_AUTHENTICATE, produces = MediaType.APPLICATION_JSON_VALUE)
    @Operation(summary = "Start authentication")
    public ResponseEntity<Object> startAuthentication(
        final Principal authenticatedPrincipal) throws Exception {

        val request = server.startAuthentication(Optional.ofNullable(authenticatedPrincipal).map(Principal::getName));
        if (request.isRight()) {
            return startResponse(new StartAuthenticationResponse(request.right().orElseThrow()));
        }
        return messagesJson(ResponseEntity.badRequest(), request.left().orElseThrow());
    }
Start authentication and provide response entity.

@return the response entity
@throws Exception the exception
support/cas-server-support-webauthn-core/src/main/java/org/apereo/cas/webauthn/web/WebAuthnController.java