Used new aliases and removed test specific code

Now that we have hostames which look like real hostnames in tests we're able to
remove test specific handling for the `isHandle` function. This also switches
us to use the new aliases everywhere in the tests for consistency

Author: allouis

features/account.feature

@@ -14,12 +14,12 @@ Feature: Account API
     And the response contains "Our" account details
 
   Scenario: Get account by handle
-    When an authenticated "get" request is made to "/.ghost/activitypub/account/@Alice@fake-external-activitypub"
+    When an authenticated "get" request is made to "/.ghost/activitypub/account/@Alice@fake-external-activitypub.test"
     Then the request is accepted with a 200
     And the response contains "Alice" account details
 
   Scenario: Get non-existent account
-    When an authenticated "get" request is made to "/.ghost/activitypub/account/@nonexistent@fake-external-activitypub"
+    When an authenticated "get" request is made to "/.ghost/activitypub/account/@nonexistent@fake-external-activitypub.test"
     Then the request is rejected with a 500
 
   Scenario: Get account without authentication