[18.0][ADD] mrp_bom_warn_message

[Tisho99]

This module allows to configure a warning on manufacturing orders when a bill of materials is selected

This module is similar as other OCA modules such as sale_order_warn_message

T-9321

[Jaimermaccione]

@Tisho99 Functionally reviewed in a local environment.

Additional validations were performed beyond the basic flow:

• BoM change on existing MO
  Changing the Bill of Materials on an existing Manufacturing Order correctly triggers the warning.

• Manufacturing Order states
  State-related checks are not applicable:

  • Cancelled Manufacturing Orders cannot be reverted.
  • Done Manufacturing Orders only allow dismantling, which does not return them to a previous state.

• BoM warning update
  Updating the warning message on the BoM is correctly reflected in already created Manufacturing Orders.

• Multiple BoMs
  For products with multiple Bills of Materials, the warning shown always corresponds to the selected BoM.

With all these checks, the module behaves as expected and the README accurately describes the verified behavior.

LGTM!

[ValentinVinagre]

LGTM 👍🏻