[FIX] base: User loses company access when merging the related contact
[FIX] base: User loses company access when merging the related contact

Issue

	- Create a second company
	- Create user with access to main and second company
	- Go to "Contacts" app
	- Edit contact of the new user, and under the "Sales & Purchases" tab,
	  ensure that the company field is set
	- Create a new contact with same email of the new user
	- In list view, select both contact related to new user
	- Click on Action->Merge Selected Contacts, then merge contacts

	User has no more access to both companies, only company related to
	merged destination Contact/Partner.

Cause

	All related companies are unliked from user, and instead overwrited
	with one company related of the merged destination Contact/Partner.

Solution

	Instead of unlink all companies, we will only add the contact company
	to the allowed companies of the user.

opw-2269397

closes odoo/odoo#52620

X-original-commit: e00b23b73f00fb24b2771ea8894031b35204e65e
Signed-off-by: Nicolas Martinelli (nim) <771435c469f83f6aa9c405ac5e1ed06314a94f2d@odoo.com>
Signed-off-by: bon-odoo <e19836c0ea27a135a9ddccf8b92fac375fd6f048@users.noreply.github.com>

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo