Configure LMS to select oauth2 providing library.

Available backends:

* django-oauth-toolkit (DOT)
* django-oauth2-provider (DOP)

* Use provided client ID to select backend for
  * AccessToken requests
  * third party auth-token exchange
* Create adapters to isolate library-dependent functionality
* Handle django-oauth-toolkit tokens in edX DRF authenticator class

MA-1998
MA-2000

lms/djangoapps/oauth_dispatch/adapters/__init__.py

@@ -0,0 +1,7 @@
+"""
+Adapters to provide a common interface to django-oauth2-provider (DOP) and
+django-oauth-toolkit (DOT).
+"""
+
+from .dop import DOPAdapter
+from .dot import DOTAdapter

lms/djangoapps/oauth_dispatch/adapters/dop.py

@@ -0,0 +1,70 @@
+"""
+Adapter to isolate django-oauth2-provider dependencies
+"""
+
+from provider.oauth2 import models
+from provider import constants, scope
+
+
+class DOPAdapter(object):
+    """
+    Standard interface for working with django-oauth2-provider
+    """
+
+    backend = object()
+
+    def create_confidential_client(self, name, user, redirect_uri, client_id=None):
+        """
+        Create an oauth client application that is confidential.
+        """
+        return models.Client.objects.create(
+            name=name,
+            user=user,
+            client_id=client_id,
+            redirect_uri=redirect_uri,
+            client_type=constants.CONFIDENTIAL,
+        )
+
+    def create_public_client(self, name, user, redirect_uri, client_id=None):
+        """
+        Create an oauth client application that is public.
+        """
+        return models.Client.objects.create(
+            name=name,
+            user=user,
+            client_id=client_id,
+            redirect_uri=redirect_uri,
+            client_type=constants.PUBLIC,
+        )
+
+    def get_client(self, **filters):
+        """
+        Get the oauth client application with the specified filters.
+
+        Wraps django's queryset.get() method.
+        """
+        return models.Client.objects.get(**filters)
+
+    def get_client_for_token(self, token):
+        """
+        Given an AccessToken object, return the associated client application.
+        """
+        return token.client
+
+    def get_access_token(self, token_string):
+        """
+        Given a token string, return the matching AccessToken object.
+        """
+        return models.AccessToken.objects.get(token=token_string)
+
+    def normalize_scopes(self, scopes):
+        """
+        Given a list of scopes, return a space-separated list of those scopes.
+        """
+        return ' '.join(scopes)
+
+    def get_token_scope_names(self, token):
+        """
+        Given an access token object, return its scopes.
+        """
+        return scope.to_names(token.scope)

lms/djangoapps/oauth_dispatch/adapters/dot.py

@@ -0,0 +1,73 @@
+"""
+Adapter to isolate django-oauth-toolkit dependencies
+"""
+
+from oauth2_provider import models
+
+
+class DOTAdapter(object):
+    """
+    Standard interface for working with django-oauth-toolkit
+    """
+
+    backend = object()
+
+    def create_confidential_client(self, name, user, redirect_uri, client_id=None):
+        """
+        Create an oauth client application that is confidential.
+        """
+        return models.Application.objects.create(
+            name=name,
+            user=user,
+            client_id=client_id,
+            client_type=models.Application.CLIENT_CONFIDENTIAL,
+            authorization_grant_type=models.Application.GRANT_AUTHORIZATION_CODE,
+            redirect_uris=redirect_uri,
+        )
+
+    def create_public_client(self, name, user, redirect_uri, client_id=None):
+        """
+        Create an oauth client application that is public.
+        """
+        return models.Application.objects.create(
+            name=name,
+            user=user,
+            client_id=client_id,
+            client_type=models.Application.CLIENT_PUBLIC,
+            authorization_grant_type=models.Application.GRANT_PASSWORD,
+            redirect_uris=redirect_uri,
+        )
+
+    def get_client(self, **filters):
+        """
+        Get the oauth client application with the specified filters.
+
+        Wraps django's queryset.get() method.
+        """
+        return models.Application.objects.get(**filters)
+
+    def get_client_for_token(self, token):
+        """
+        Given an AccessToken object, return the associated client application.
+        """
+        return token.application
+
+    def get_access_token(self, token_string):
+        """
+        Given a token string, return the matching AccessToken object.
+        """
+        return models.AccessToken.objects.get(token=token_string)
+
+    def normalize_scopes(self, scopes):
+        """
+        Given a list of scopes, return a space-separated list of those scopes.
+        """
+        if not scopes:
+            scopes = ['default']
+        return ' '.join(scopes)
+
+    def get_token_scope_names(self, token):
+        """
+        Given an access token object, return its scopes.
+        """
+        return list(token.scopes)