Keep selections aliased as join columns in withGraphFetched() and relation queries (#111)

[lehni]

What

withGraphFetched() and relation queries (RelationFindOperation) treat a selection without a column, of an aggregate, raw SQL or a subquery, as selecting the column that its alias names, like max('ownerId as ownerId'), raw('?? as ??', ['ownerId', 'ownerId']) or a subquery .as('ownerId'). They don't select that join column once more. The rule lives in one helper in Selection.js, used where these queries check for missing join columns. findSelection(), hasSelection() and hasSelectionAs() are unchanged, so withGraphJoined() keeps its strict id check: an aggregate, raw SQL or subquery selected under the name of an id column, like max('pets.id as id'), still throws.

Why

Aggregates are meant to select only their aliases since #111, and raw SQL and subqueries with an alias select only that alias too, but nothing matched these aliases. For a query like Pet.query().max('ownerId as ownerId').groupBy('ownerId').withGraphFetched('owner'), withGraphFetched() selected ownerId a second time as an internal selection and then removed it from the result, so the selected value was gone.

The alias only counts where objection reads the join columns from the result rows. In withGraphJoined(), such a selection under an id name would be used as the root model's id, so it stays an error there.

Tests

• Integration: should keep an aggregate aliased as the join column (#111) fails on next.
• Integration: should keep raw and subquery selections aliased as the join column (#111) fails with only aggregates matched.
• Unit: should throw if the user selects raws, subqueries or aggregates under the names of the ids also checks max('pets.id as id').

Part of #53.