Partial ActiveBehaviour fix for junction tables

[SpawnCycle]

PR Info

Partially fixes the odd behavior with junction tables when using ActiveModelEx
Couldn't figure out how to make after_save work

• (Almost) Closes ActiveModelEx odd ActiveModelBehavior with a junction table #3010

Bug Fixes

• ActiveModelBehavior is now triggered for the junction table when adding a via model

Changes

• Adds a Send constraint in the establish links function
• Adds before_save function call on the active model
• Adds before/after_delete function call on the active model

[SpawnCycle]

While exploring the repo I saw near-identical code in sea-orm-sync, should I add the changes to it too?

[Huliiiiii]

It has been fixed on master. You can just rebase.

[SpawnCycle]

Will do, but what about establish_links in sea-orm-sync?

[Huliiiiii]

You can run build-tools/make-sync.sh to sync changes.

[SpawnCycle]

Mysql and mariadb don't support returning syntax, so as it is currently the after_save won't run on them