[FIX] web: BasicModel: don't update default one2many records

Let's assume a one2many field in a form view with a default value
with commands 4 (link to). Before this rev., when saving the record,
the BasicModel generated a command 4 and a command 1 (update) for
each record, with the values of the record (directly coming from DB).
This can cause an issue when the related record can't be edited
(e.g. a posted journal entry in accounting).

closes odoo/odoo#33797

Signed-off-by: Quentin De Paoli (qdp) <qdp@openerp.com>

addons/web/static/src/js/views/basic/basic_model.js

@@ -3175,7 +3175,7 @@ var BasicModel = AbstractModel.extend({
                                 commands[fieldName].push(x2ManyCommands.link_to(list.res_ids[i]));
                                 continue;
                             }
-                            changes = this._generateChanges(relRecord, options);
+                            changes = this._generateChanges(relRecord, _.extend({}, options, {changesOnly: true}));
                             if (!this.isNew(relRecord.id)) {
                                 // the subrecord already exists in db
                                 commands[fieldName].push(x2ManyCommands.link_to(relRecord.res_id));

addons/web/static/tests/fields/relational_fields/field_many2one_tests.js

@@ -1676,9 +1676,7 @@ QUnit.module('fields', {}, function () {
                     obj.turtles,
                     [
                         [4, 2, false],
-                        [1, 2, { turtle_foo: 'blip' }],
                         [4, 3, false],
-                        [1, 3, { turtle_foo: 'kawa' }]
                     ],
                     "should have properly created the x2many command list");
             };
@@ -1702,14 +1700,9 @@ QUnit.module('fields', {}, function () {
                         return Promise.resolve({ turtles: [[6, 0, [2, 3]]] });
                     }
                     if (args.method === 'create') {
-                        // it would be even better if we did not send the current
-                        // unchanged state with the command 1, but this seems more
-                        // difficult.
                         assert.deepEqual(args.args[0].turtles, [
                             [4, 2, false],
-                            [1, 2, { turtle_foo: 'blip' }],
                             [4, 3, false],
-                            [1, 3, { turtle_foo: 'kawa' }]
                         ], 'should send proper commands to create method');
                     }
                     return this._super.apply(this, arguments);