add authenticated User LangPreference tracking

+ Use User.LangPreference when there is no set AURSID
  if request.user.is_authenticated is true.
+ Updated post /language to update LangPreference when
  request.user.is_authenticated.
+ Restore language during test where we change it.
+ Added the user attribute to aurweb.testing.requests.Request.

Signed-off-by: Kevin Morris <kevr@0cost.org>

aurweb/testing/requests.py

@@ -1,8 +1,27 @@
+import aurweb.config
+
+
+class User:
+    """ A fake User model. """
+    # Fake columns.
+    LangPreference = aurweb.config.get("options", "default_lang")
+
+    # A fake authenticated flag.
+    authenticated = False
+
+    def is_authenticated(self):
+        return self.authenticated
+
+
 class Client:
+    """ A fake FastAPI Request.client object. """
+    # A fake host.
     host = "127.0.0.1"
 
 
 class Request:
+    """ A fake Request object which mimics a FastAPI Request for tests. """
     client = Client()
     cookies = dict()
     headers = dict()
+    user = User()