[19.0][MIG] product_sequence: Migration to 19.0

[bosd]

Supersedes #2127.

Migration of product_sequence to 19.0, redone from scratch with the standard
OCA migration procedure. The 19.0 migration commit of @fd-oerp is cherry-picked
(with -x) so their authorship and work are preserved, and they have been added
to readme/CONTRIBUTORS.md.

Why redo it

• [19.0][MIG] product_sequence: Migration to 19.0 #2127 squashed the administrative commits into the functional commits, so
  several [MIG]/[IMP] commits ended up carrying the bodies of unrelated
  .pot/README/Weblate commits, blurring the attribution of the real changes.
• It was branched off an older 18.0, so it did not carry
  [IMP] product_sequence: default_code shouldn't be mandatory nor the Turkish,
  Croatian, Catalan and Slovenian translations that landed on 18.0 since.

Migration changes

• test_product_category_sequence: since 19.0, categ_id is no longer required
  on product.template, so assertTrue(product_4.categ_id) no longer holds.
  Rather than dropping the case (as [19.0][MIG] product_sequence: Migration to 19.0 #2127 did), it now asserts what the module
  actually guarantees: a product without category falls back on the default
  product sequence.

On top of the plain migration

• New OCA icon ([IMP] product_sequence: use the new OCA icon), the one
  already used by other addons of this repository.

• Demo data ([ADD] product_sequence: demo data), illustrating the three
  ways a reference is assigned:

  Product	Category	Reference
  Floor Lamp	Lamps (prefix LAMP)	LAMP00001
  Desk Lamp	Desk Lamps (no prefix, child of Lamps)	LAMP00002
  Office Chair	Furniture (prefix FURN)	FURN00001
  Extension Cord	none	PR/00001

  The parent-category fallback is enabled on the main company so the Desk Lamp
  case is actually demonstrated; test_product_parent_category_sequence
  therefore now disables that setting explicitly instead of relying on the
  ambient company configuration.

  Three tests assert the demo references. They skip when the database has no
  demo data, which is the case on the CI since Odoo 19.0 does not load demo data
  by default.

@fd-oerp thanks for the original migration.
the history rework could not be done as a review suggestion. @NICO-SOLUTIONS the
copy() discussion from #2127 is deliberately left out of this PR to keep the
migration reviewable; happy to open a follow-up for it.

[bosd]

Pushed a follow-up to get Codecov green.

Two things came out of it:

1. The demo tests no longer skip. Since 19.0 Odoo does not load demo data by default, so the CI databases have none and the tests were skipped there. They now load the demo files themselves via convert_file(..., mode="init", noupdate=True) when the records are missing, so the demo data is actually validated on the CI. Verified both ways: with and without --with-demo.

2. copy() was broken and is fixed ([FIX] product_sequence: keep the reference of copied products). This is why the two copy tests had to be disabled in 63a0f5b "[FIX] product_sequence: disable test", and it is the thread @NICO-SOLUTIONS opened on #2127.

Since odoo/odoo#38303 (14.0), copying a product.product does not copy the variant: the template is copied and its first variant returned. That variant is built by _create_variant_ids with no reference, so it gets a fresh sequence number and the default_code the override put into default was silently discarded:

• copying PROD02 produced PR/00007 instead of PROD02-copy;
• product.copy({"default_code": "REF"}) ignored REF entirely.

The override now restores the requested reference on the new variant after the copy, and both tests are re-enabled. Added tests for the no-source-reference case (copy just gets a new sequence number, no -copy suffix) and for the multi-variant case (the reference stays on the variant and is not pushed up to the template).

@NICO-SOLUTIONS if you would rather have a copy always take a fresh sequence number instead of the -copy suffix, that is a one-line change from here let me know and i will change it.

[Reyes4711-S73]

LGTM

[NICO-SOLUTIONS]

@NICO-SOLUTIONS if you would rather have a copy always take a fresh sequence number instead of the -copy suffix, that is a one-line change from here let me know and i will change it.

@bosd
Thanks for tackling this and for the explanation of the Odoo core change behind it.

From my point of view, a copied product should receive a fresh sequence number instead of keeping the -copy suffix. default_code should identify the new product and not describe how the record was created.

I can see the benefit of the -copy suffix for temporary drafts or work copies, as it makes the origin of a duplicate immediately visible. On the other hand, if a user wants a new sequence-generated reference, this can already be achieved by setting default_code to /, but this requires an additional manual step.

However, I would not expect the -copy suffix to remain as the final product reference used in sales, purchasing, inventory, or integrations.

This is just my perspective though; I won´t make this decision alone. I am happy to follow the consensus of the maintainers/contributors here. If there are other advantages of keeping the -copy behavior, I would be interested to understand them.

If this is handled in a separate follow-up PR, that is also fine for me. However, I think we should define a clear approach for this scenario.

I'll review the code once I find some time.