Run the internal reads of BelongsToManyRelation writes without find hooks (#2667)

[lehni]

What

The reads that relate(), unrelate(), insert() and delete() through a BelongsToManyRelation run to keep the arrays of keys up to date (findKeys() and updateKeys()) use findOptions({ dontCallFindHooks: true }). dontCallFindHooks now also skips the static beforeFind hook, not only afterFind and $afterFind(), so these reads call no find hooks at all. The writes still call the owner's update hooks.

Why

These reads are no finds of the user, but they called the user's static beforeFind and afterFind with partial models and the relation's hook arguments, and used what afterFind returned as their data. An afterFind that filters rows, e.g. for soft deletes or access control, made relate() resolve to 0 without writing anything.

Breaking

dontCallFindHooks is internal. The other queries that use it, fetchGraph() / $fetchGraph() on the models it's given and the relations that skipFetched skips, no longer call the static beforeFind of these models. They already didn't call afterFind: the find hooks are only called for queries that run. The changelog lists it under Breaking changes next to the outer upsertGraph() queries, and the static hooks section of the migration guide says so.

Tests

• relate(), unrelate(), insert() and delete() should not call the find hooks with beforeFind and filtering afterFind hooks on the owner and related model classes.
• should not call the find hooks of the root class in fetchGraph() also checks beforeFind.

Both fail without the change.

Part of #53.