use base58 for slugs to remove doubt

app/models/order.py

@@ -11,9 +11,11 @@ from utils import first
 from .database import db
 from .user import User
 
+BASE58_ALPHABET = \
+    b'123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
+
 def generate_slug():
-    alphabet = string.ascii_letters + string.digits
-    secret = ''.join(secrets.choice(alphabet) for i in range(7))
+    secret = ''.join(secrets.choice(BASE58_ALPHABET) for i in range(7))
     while Order.query.filter(Order.slug == secret).first() is not None:
         secret = ''.join(secrets.choice(alphabet) for i in range(7))
     return secret