Add username to cache key in datasource renderer if OAuth2 is used

(fixes #5849)

README

@@ -162,6 +162,9 @@ A source definition is a dictionnary containing the following keys:
       as keyword arguments to the `reader()` or `DictReader()`
       constructors, depending on whether the `fieldnames` arguments is
       present,
+    - `user_context`, whether the user must be part of the cache key. For retro
+      compatibility If authentication mechanism is OAuth2, it defaults to True
+      otherwise to False.
 
 Exemple with the JSON parser
 ----------------------------

src/cmsplugin_blurp/renderers/data_source.py

@@ -141,9 +141,14 @@ class Data(object):
         self.signature_key = source.get('signature_key')
         self.parser_type = source.get('parser_type', 'raw')
         self.content_type = source.get('content_type', self.MAPPING[self.parser_type])
+        self.user_context = source.get('user_context',
+                config.get('user_context', self.auth_mech == 'oauth2'))
         pre_hash = 'datasource-{self.slug}-{self.url}-{self.limit}-' \
                 '{self.refresh}-{self.auth_mech}-{self.signature_key}' \
                 .format(self=self)
+        # If authentication is used
+        if self.user_context:
+            pre_hash += '-%s' % unicode(self.request.user).encode('utf-8')
         self.key = hashlib.md5(pre_hash).hexdigest()
         self.now = time.time()
         self.__content = self.__CACHE_SENTINEL