Fix for WrapMysqlModifySubqueryTransformation when using join builder

[marcinlee]

Fixes error where .onIn()/.andOnIn() causes:
TypeError: parentQuery.isUpdate is not a function

This happens when we provide .onIn() with an objection query.

BlogPost.query(db)
  .alias('post')
  .innerJoin('post.comment', (join) => {
    join.onIn(
      'comment.author_id',
      Author.query(db).where('active', true)
    );
  });

Since WrapMysqlModifySubqueryTransformation does not make sense for join query, we simply skip it for JoinBuilder.

Note: This wasn't an issue in objection v1 and this error does not happen if we provide .onIn() with knex query instead.

[falkenhawk]

thanks for the PR!

[falkenhawk]

isn't it a slight over-optimization? Wouldn't this suffice? :)

Suggested change

	const getJoinBuilder = once(() => require('../JoinBuilder').JoinBuilder);
	const { JoinBuilder } = require('../JoinBuilder');

[falkenhawk]

ok it seems it is necessary - same logic is in

objection.js/lib/queryBuilder/operations/ObjectionToKnexConvertingOperation.js

Line 7 in 412bb77

const getJoinBuilder = once(() => require('../JoinBuilder').JoinBuilder);