[WIP] Add unique indexes for containers tables #15308

Add :deleted to the disconnectable Containers tables, which will allow us to mark soft deleted records.

Change disconnected Containers records to soft deleted, reconnecting the old_ems_id if possible.

Specs for changing disconnected Containers records to soft deleted

Add partial index to :deleted col to speedup queries. It has to be a partial index, otherwise the cost is too high and PG will not pick it.

Fix the comment :deleted => true goes to :ems_id => nil

Use only :deleted_on column for soft_delete, where :deleted_on => nil marks not deleted record.

Scope ems relations to show only :deleted => false, which mimics the missing :ems_id foreign key we had before, doing disconnect ems.

Do soft delete using :deleted => true instead of doing ems disconnect by setting :ems_id => nil

Add scopes for deleted not deleted to the archived mixin, we should always use a scope, rather than a specific query.

Alias archived? to deleted?

Use :active, :archived scopes and methods for soft-delete

Use only :deleted_on for a soft-delete

Move dependent destroy to _all relations, since we want to cascade deleted both active and archived records.

Remove duplicate :container_definitions relation, we already have it defined using :ems_id foreign key

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