Reject self-boosts

These are easily abused by spammers

announce.py

@@ -32,6 +32,8 @@ def outboxAnnounce(recentPostsCache: {},
     """
     if not messageJson.get('actor'):
         return False
+    if not isinstance(messageJson['actor'], str):
+        return False
     if not messageJson.get('type'):
         return False
     if not messageJson.get('object'):
@@ -39,6 +41,8 @@ def outboxAnnounce(recentPostsCache: {},
     if messageJson['type'] == 'Announce':
         if not isinstance(messageJson['object'], str):
             return False
+        if messageJson['actor'] in messageJson['object']:
+            return False
         nickname = getNicknameFromActor(messageJson['actor'])
         if not nickname:
             print('WARN: no nickname found in ' + messageJson['actor'])