feat(relations): support macro ?TableAlias in relation callback

[fiftin]

Relates to #557

Add ability to use macro ?TableAlias to substitution related table alias.

Example:

var card Card
db.NewSelect().Model(&card).
    Relation("Card.Deck.Collection", func(query *bun.SelectQuery) *bun.SelectQuery {
        return query.Where("?TableAlias.name = ?", collectionName)
    })

[vmihailenco]

Thanks for the effort, but we need to find a solution that does not involve using regexps. I guess we need to bind the fmter to use the right model when appending relations...

[fiftin]

@vmihailenco Fixed

[fiftin]

Hi @vmihailenco Please check the PR.

[vmihailenco]

Hi @fiftin,

I still have plans to look at this when time allows. Sorry for the delay.

[fiftin]

I created this PR for MTS contest only, contest finished. Thank you. I don't want you to merge the PR and use the code.