When baker.make() is called with _bulk_create=True and a M2M field is
specified via double-underscore FK lookup syntax (e.g. home__dogs=[dog]),
the M2M relationship was never applied to the saved FK object.

Root cause: during the prepare() phase, baker correctly stores M2M values
in the sub-baker's m2m_dict, but _handle_m2m() is gated behind `if _commit:`
and therefore never executes in the bulk_create path. Subsequently,
_save_related_objs() only saves FK rows and makes no M2M calls. The two
existing M2M loops in bulk_create() scan only the top-level model's direct
and reverse M2M fields, neither of which covers the fk__m2m kwarg pattern.
The net result is that home.dogs.set([dog]) is never called, leaving the
M2M relation empty in the database.

Fix: after all entries have been bulk-created and FK objects saved, inspect
the kwargs dict for double-underscore patterns of the form fk_field__m2m_field.
For each pattern where the prefix resolves to a ForeignKey or OneToOneField
on the current model and the suffix resolves to a ManyToManyField on the
related model, call .set() on the FK object for every created entry.

Only auto-created through models are supported; fields using a custom
through= model are skipped since they require explicit through instance
creation with extra field values baker cannot infer.

FieldDoesNotExist is caught specifically (not bare Exception) so that
unexpected errors still surface rather than being silently swallowed.

Changes:
- model_bakery/baker.py: import FieldDoesNotExist from django.core.exceptions;
  add FK-nested M2M handling loop at the end of bulk_create() with specific
  exception handling and auto-created through model guard
- tests/generic/models.py: add HomeOwner model with ForeignKey to Home,
  providing the minimal fixture required to reproduce the reported scenario
- tests/test_baker.py: add test_create_through_foreign_key_field to
  TestCreateM2MWhenBulkCreate, reproducing the exact scenario from the issue
  (baker.make(HomeOwner, home__dogs=[dog], _quantity=10, _bulk_create=True))

Fixes model-bakers#490

Author: Benjamin Aduo (@benaduo)

I actually like this. Yes lets do this

Co-authored-by: Rust Saiargaliev <hey@amureki.me>

Hmmm... I wanted to be very thorough in my docs ... but yeah I see how this can be harder to read... very nice catch

Co-authored-by: Rust Saiargaliev <hey@amureki.me>

This will indeed lead to less db hits... i agree

Co-authored-by: Rust Saiargaliev <hey@amureki.me>