models: Add new helper can_move_messages_between_streams.

This commit adds new helper can_move_messages_between_streams
which will be used to check whether a user is allowed to move
messages from one stream to another according to value of
'move_messages_between_streams_policy'.

zerver/models.py

@@ -1554,6 +1554,7 @@ class UserProfile(AbstractBaseUser, PermissionsMixin):
             "create_stream_policy",
             "invite_to_stream_policy",
             "invite_to_realm_policy",
+            "move_messages_between_streams_policy",
         ]:
             raise AssertionError("Invalid policy")
 
@@ -1588,6 +1589,9 @@ class UserProfile(AbstractBaseUser, PermissionsMixin):
     def can_invite_others_to_realm(self) -> bool:
         return self.has_permission("invite_to_realm_policy")
 
+    def can_move_messages_between_streams(self) -> bool:
+        return self.has_permission("move_messages_between_streams_policy")
+
     def can_access_public_streams(self) -> bool:
         return not (self.is_guest or self.realm.is_zephyr_mirror_realm)
 

zerver/tests/test_message_edit.py

@@ -1539,6 +1539,13 @@ class EditMessageTest(ZulipTestCase):
             to_invite_only=False,
         )
 
+    def test_can_move_messages_between_streams(self) -> None:
+        def validation_func(user_profile: UserProfile) -> bool:
+            user_profile.refresh_from_db()
+            return user_profile.can_move_messages_between_streams()
+
+        self.check_has_permission_policies("move_messages_between_streams_policy", validation_func)
+
 
 class DeleteMessageTest(ZulipTestCase):
     def test_delete_message_invalid_request_format(self) -> None: