FIXES FRMW-2878
**What**
Currently, the `one-to-one` unique constraints does not account for deleted record. This prevents from inserting a new record wth the same fk if another one is deleted.
**Caveat**
`hasOne` with FK option is meant to be a special case, for example a many to one - one to many without defining the other side of the relation. In that case we don't handle this behaviour and keep it as it is
This also includes rework of the currency model for the Store module.
This change is breaking as existing stores won't have any supported currencies set, so users would need to go to the store settings again and choose the supported currencies there.
