A recurring event with a start date and a time duration had a wrong start and
stop date computed.
Introduced at 76b724294a.
Previously the r_date contained only the start_date but now it contains both
start and stop dates. This implies that the method 'get_recurrent_ids' could
use 'get_search_fields' with a stop_date (depending on the domain order) and
returns incorrect dates.
This commit ensure to launch the get_search_fields with the start date.
Closes#15922
Add a 3 use cases with tests that were failing before.
datetime filters were not working correctly on stop filters
The `_get_recurrent_date_by_event` was only computing recurrency on the start
field of an event which can make a difference. A recurring event
start=2017-01-01 09:00:00; stop=2017-01-01 10:00:0
was not matched in a search ('stop', '>', '2017-01-01 09:30:00')
The filter != was not handled in the recurring use cases.
e.g. making the search 'start is set' in the web client is equal to
('start', '!=', False)
Searching with only a start filter matching recurring events but not the
first ("real") occurence, was returning no result if no stop filter was present.
start=2017-01-01 09:00:00; count=5
had no result in a search ('start', '>', '2017-01-02')
amoyaux