SAMLInternalResponse for saml backend

Adds a SAMLInternalResponse class that the saml backend returns instead
of the parent class InternalResponse. The new class allows SAML specific
details to be added into the response that is later passed into
plugins/microservices. The first SAML specific detail added is the SAML
NameID if it is asserted by the IdP that sent the response.

Author: skoranda

src/satosa/backends/saml2.py

@@ -214,10 +214,16 @@ def _translate_response(self, response, state):
         issuer = response.response.issuer.text
 
         auth_info = AuthenticationInformation(auth_class_ref, timestamp, issuer)
-        internal_resp = InternalResponse(auth_info=auth_info)
+        internal_resp = SAMLInternalResponse(auth_info=auth_info)
 
         internal_resp.user_id = response.get_subject().text
         internal_resp.attributes = self.converter.to_internal(self.attribute_profile, response.ava)
+        
+        # The SAML response may not include a NameID
+        try:
+            internal_resp.name_id = response.assertion.subject.name_id
+        except AttributeError:
+            pass
 
         satosa_logging(logger, logging.DEBUG, "received attributes:\n%s" % json.dumps(response.ava, indent=4), state)
         return internal_resp
@@ -315,3 +321,32 @@ def get_metadata_desc(self):
 
             entity_descriptions.append(description)
         return entity_descriptions
+
+class SAMLInternalResponse(InternalResponse):
+    """
+    Like the parent InternalResponse, holds internal representation of 
+    service related data, but includes additional details relevant to
+    SAML interoperability.
+
+    :type name_id: instance of saml2.saml.NameID from pysaml2
+    """
+    def __init__(self, auth_info=None):
+        super().__init__(auth_info)
+
+        self.name_id = None
+
+    def to_dict(self):
+        """
+        Converts a SAMLInternalResponse object to a dict
+        :rtype: dict[str, dict[str, str] | str]
+        :return: A dict representation of the object
+        """
+        _dict = super().to_dict()
+
+        if self.name_id:
+            _dict['name_id'] = {self.name_id.format : self.name_id.text}
+        else:
+            _dict['name_id'] = None
+
+        return _dict
+