Merge and modify PR from @Kurnihil

Merging a PR from @Kurnihil into the already rebased branch.
Made some small changes to make it work with newer changes.

Some finetuning is probably still needed.

Co-authored-by: Daniele Andrei <daniele.andrei@geo-satis.com>
Co-authored-by: Kurnihil

src/db/schemas/mysql/schema.rs

@@ -204,6 +204,7 @@ table! {
         client_kdf_parallelism -> Nullable<Integer>,
         api_key -> Nullable<Text>,
         avatar_color -> Nullable<Text>,
+        external_id -> Nullable<Text>,
     }
 }