feat: several endpoint types can be registered

AuthorizationServer.register_endpoint can be called several times for
one kind of endpoint.

authlib/oauth2/rfc6749/authorization_server.py

@@ -3,6 +3,7 @@
 from .errors import (
     OAuth2Error,
     InvalidScopeError,
+    ContinueIteration,
     UnsupportedResponseTypeError,
     UnsupportedGrantTypeError,
 )
@@ -186,7 +187,8 @@ def register_endpoint(self, endpoint_cls):
 
         :param endpoint_cls: A endpoint class
         """
-        self._endpoints[endpoint_cls.ENDPOINT_NAME] = endpoint_cls(self)
+        endpoints = self._endpoints.setdefault(endpoint_cls.ENDPOINT_NAME, [])
+        endpoints.append(endpoint_cls(self))
 
     def get_authorization_grant(self, request):
         """Find the authorization grant for current request.
@@ -231,12 +233,15 @@ def create_endpoint_response(self, name, request=None):
         if name not in self._endpoints:
             raise RuntimeError(f'There is no "{name}" endpoint.')
 
-        endpoint = self._endpoints[name]
-        request = endpoint.create_endpoint_request(request)
-        try:
-            return self.handle_response(*endpoint(request))
-        except OAuth2Error as error:
-            return self.handle_error_response(request, error)
+        endpoints = self._endpoints[name]
+        for endpoint in endpoints:
+            request = endpoint.create_endpoint_request(request)
+            try:
+                return self.handle_response(*endpoint(request))
+            except ContinueIteration:
+                continue
+            except OAuth2Error as error:
+                return self.handle_error_response(request, error)
 
     def create_authorization_response(self, request=None, grant_user=None):
         """Validate authorization request and create authorization response.

authlib/oauth2/rfc6749/errors.py

@@ -32,6 +32,8 @@
 """
 from authlib.oauth2.base import OAuth2Error
 from authlib.common.security import is_secure_transport
+from authlib.common.errors import AuthlibBaseError
+
 
 __all__ = [
     'OAuth2Error',
@@ -42,6 +44,7 @@
     'MissingAuthorizationError', 'UnsupportedTokenTypeError',
     'MissingCodeException', 'MissingTokenException',
     'MissingTokenTypeException', 'MismatchingStateException',
+    'ContinueIteration',
 ]
 
 
@@ -231,3 +234,7 @@ class MissingTokenTypeException(OAuth2Error):
 class MismatchingStateException(OAuth2Error):
     error = 'mismatching_state'
     description = 'CSRF Warning! State not equal in request and response.'
+
+
+class ContinueIteration(AuthlibBaseError):
+    pass