[16.0][MIG] sale_commission_product: Migration to 16.0

[odooNextev]

I don't know exactly if it can be defined as a migration itself, but I started from sale_commission_product module for this project, I kept commits history and mostly the goal of my module is the same as initial version 8.0.

In fact this module allows users to set dedicated agents on product.template (unlike 8.0 version which added the agent field on product.product) and they will find in sale.order.line both agents on SO partner and agents on SOL product.

Talking about computation, I simplified what was done in 8.0 version and I hope it can be enough. In particular I only extended _prepare_agents_vals_partner method to add product agents to partner agents array returned from original sale_commission method. To trigger this method on product changing, I had to add @api.depends("product_id") to _compute_agent_ids of sale.order.line and account.move.line. By the way, I followed what was done in 8.0 version and I added account section even if _compute_agent_ids method of account.move.line it's inside account_commission and not in sale_commission. Alternatively we could change the module name to include "account" or create a separated module like account_commission_product, but I don't know if it's worth it. Anyway I added account_commission to depends.