This allows to fetch merged opening hours instead of actually edited
opening hours.
They will be merged per valid time span.
The data structure is a bit different as each time span has a list of
week days, each with its own open and end.
Relates: #10246
Not all things are managed by TouristMarketingCompany, some are managed
by generic organisations.
Those are now handled the same way as TouristMarketingCompany are
already handled.
That way those things can also be imported, as they now can import their
manager.
