Alternatives to #main-key

See https://datatracker.ietf.org/doc/html/rfc6901#section-6

cache.py

@@ -149,6 +149,8 @@ def get_person_pub_key(base_dir: str, session, person_url: str,
         return None
     if '#/publicKey' in person_url:
         person_url = person_url.replace('#/publicKey', '')
+    elif '/main-key' in person_url:
+        person_url = person_url.replace('/main-key', '')
     else:
         person_url = person_url.replace('#main-key', '')
     users_paths = get_user_paths()

person.py

@@ -923,6 +923,8 @@ def person_lookup(domain: str, path: str, base_dir: str) -> {}:
     """
     if path.endswith('#/publicKey'):
         path = path.replace('#/publicKey', '')
+    elif path.endswith('/main-key'):
+        path = path.replace('/main-key', '')
     elif path.endswith('#main-key'):
         path = path.replace('#main-key', '')
     # is this a shared inbox lookup?