membership unit test checks joinability and player limit; post.create() checks allow_post

amanuensis/backend/membership.py

@@ -41,13 +41,14 @@ def create(
     lex: Lexicon = db(
         select(Lexicon).where(Lexicon.id == lexicon_id)
     ).scalar_one_or_none()
+    assert lex, "could not find lexicon"
 
-    # Verify lexicon is joinable; current no Lexicons are joinable so this is commented out
+    # Verify lexicon is joinable
     if not lex.joinable:
         raise ArgumentError("Can't join: Lexicon is not joinable")
 
     # Verify lexicon is not full
-    if lex.player_limit:
+    if lex.player_limit is not None:
         if (
             db(select(func.count()).where(Membership.lexicon_id == lexicon_id)).scalar()
             >= lex.player_limit