Laravel HasMany across multiple connections

I want to retrieve Offers related to Offer on a second table offer_related because I can't change the schema of the Offer table.

I have two databases on different connections, offers on one, and offer_related on another.

For the sake of argument, I'm going to name databases as follows for clarity in my examples with regards to which can change and which can't.

• database containing offers henceforth known as immutable
• database containing offer_related henceforth known as mutable

Example schema is as follows

connection1.mutable.offer_related

offer_id | related_offer_id
---------------------------
1        | 2
1        | 3

connection2.immutable.offers

id | name
---------------------------
1  | foo
2  | bar
3  | baz

I'm assuming it'd be a belongsToMany relationship, but I can't seem to get it right.

return $this->belongsToMany(Offer::class, 'immutable.offer', 'id');

// Syntax error or access violation: 1066 Not unique table/alias: 'offer'

I've also tried to manually build out a belongsToMany relationship with a custom query with no success.

I'd like to be able to call

Offer::find(1)->related; // Offer(2), Offer(3)

Any insight would be much appreciated.

via Chebli Mohamed