Add lateral join methods

I’ve been monkey-patching knex to include some lateral join methods but it’d be nice if the library actually supported them. Adding some kind of extra parameter to the existing join methods would be a potentially breaking change, not to mention the existing method signatures aren’t all compatible (lateral joins have to use a subquery). So I propose adding 8 additional methods:

• innerJoinLateral
• leftJoinLateral
• leftOuterJoinLateral
• rightJoinLateral
• rightOuterJoinLateral
• outerJoinLateral
• fullOuterJoinLateral
• crossJoinLateral

Signatures would look something like:

(raw: Raw): QueryBuilder;
(subquery: QueryCallback, on: JoinCallback): QueryBuilder;
(subquery: QueryCallback, on: Raw): QueryBuilder;
(subquery: QueryCallback, columns: { [key: string]: string | number | boolean | Raw }): QueryBuilder;
(subquery: QueryCallback, column1: string, column2: string): QueryBuilder;
(subquery: QueryCallback, column1: string, column2: Raw): QueryBuilder;
(subquery: QueryCallback, column1: string, operator: string, column2: string): QueryBuilder;

I can try to put together a PR, but I wanted to confirm this sort of change would be acceptable first.

[ghost]

And MySQL 8 seems support it too, at least I am using this query without troubles:

SELECT e0.id, e1.* FROM gallery AS e0 LEFT JOIN LATERAL (
    SELECT e2.* FROM photo AS e2 WHERE e2.gallery_id = e0.id LIMIT ?
) AS e1 ON e0.id = e1.gallery_id WHERE gallery_id IN (?)

[elhigu]

Yep it would. If we can come up with some abstraction, which works in multiple databases more work is needed to investigate how exactly each DB supports it and design some API for it which can be supported by most of the drivers.