Mixed view_only in multiple data_source_groups blocks query executions

[yanenok]

A user belonging to multiple groups that have access to one data source but with different access levels can not execute queries on that data source.

For example, if a user belongs to built-in default group and you have set view_only for all data sources in this group to true, adding this user to a new group to allow full access to one of the data sources will not work.

This is caused by group_level definition in def has_access() in permissions.py:

required_level = 1 if need_view_only else 2
group_level = 1 if any(flatten([object_groups[group] for group in matching_groups])) else 2

return required_level <= group_level

[arikfr]

Thanks!
Fixed in #1110.