stock_available_to_promise_release : refactor for proper support of moves merging

[jbaudoux]

There are several issues regarding moves merging.
The main issue is that the flag need_release is put on the delivery move when we run pull (so in pick/ship, when we pull the pick).

The problems are:

• After the delivery move is created, action_confirm is called. Odoo then call inside action_confirm the merge moves. At this stage, the need_release flag is not yet set. This could cause a non released moves to get merged to a released one. When run pull is called, we set the need_release flag but it the move was merged with a released move, then we mark again an already released quantity as to release.
• The release configuration needs to be put on the pulled rule's route (like pick) instead of on the delivery rule's route. This is counter-intuitive.

There have been some workarounds:

• [16.0][IMP] stock_available_to_promise_release: Unrelease when merging moves #834
• [16.0][IMP] stock_available_to_promise_release: Improved release process ro… #939
  but the issue is not tackled from the ground.

Also when a move is partially available, it is split (see release_split) to mark the released move as need_release=False and the remaining quantity in the new move as need_release=True. When the available quantity increases, the moves should be merged back. This causes currently an incompatibility with rma_sale where the sales rma wizard expects a unique done delivery move per transfer for the SO line. https://github.com/OCA/rma/blob/16.0/rma_sale/wizard/sale_order_rma_wizard.py#L173

Affected versions: all versions

To Do

Open a fix PR on v16

• refactor to flag need release before action confirm and read config from the delivery rule's route
• add need_release is the list of fields preventing moves merging
• revert [16.0][IMP] stock_available_to_promise_release: Unrelease when merging moves #834 but keep tests
• ensure compatibility with stock_picking_group_by_partner_by_carrier
• call moves merge after move releasing
• check pulled moves are merged (seems not the case if available quantity increases and a second release occurs)

Add your remarks or attention points @rousseldenis @lmignon @sebalix @mt-software-de