The call to web_read_group done in _loadGroups was incorrect when the first groupby
was of the form date_field:granularity (e.g. "create_date:day"). The groupby was
sent as a mesure and interpreded as such, leading to an error of the form
"Invalid aggregation function ...".
This was not detected before by lack of manual testing: the mock server used in tests
checks the read group parameters in a different way from what is done server side.
So the error was not visible in the testing environment.
In this commit, we remove the error in web_read_group and improve the mock server
(a bit) so as to make such errors be detected.
Part-of: odoo/odoo#92475
Mathieu Duckerts-Antoine
dcbf2119fc