fix a bug where calculOccurence() would return dates outside the input range when called on an event with includeDates

[hlehoux2021]

Description

This PR solves the problem where calculOccurrence() would return dates outside the input range when called on an event with includeDates

Suggested changelog entry

1. do not include in the result of calculOccurence() dates of the event that are outside the input startDate/endDate
2. when an input range is not provided, keep dates included

Types of changes

• Bug fix (non-breaking change which fixes)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
  • This change is only breaking for integrators, not for external standards or end-users.
• Documentation improvement

PR checklist

• I have checked there is no other PR open for the same change.
• I have read the [La ligne directrice pour contribuer à ce projet / Contribution guidelines for this project).
• I grant the project the right to include and distribute the code under the GNU.
• I have added tests to cover my changes.
• I have verified that the code complies with the projects coding standards.
• [Required for new sniffs] I have added MD documentation for the sniff.

[hlehoux2021]

Been in test since mid-december 25.

[Mips2648]

Could you please explain use cases causing issues?
I do see the point to not return such dates but we need to be able to reproduce to confirm the bug and the resolution, it is a bit difficult to accept PR without any background, this is probable why it is not yet validated

[hlehoux2021]

Yes, thank you!
Here is the use-case i'm in:
I use calculOccurence() to evaluate if a given calendar event will occur "tomorrow".
For this i have added to data/php/user.function.class.php this function:

public static function isTomorrow($_id) {
$event = calendar_event::byId($_id);
$startDate = (new DateTime('tomorrow'))->format('Y-m-d H:i:s');
$endDate = (new DateTime('tomorrow +1 day - 1 second'))->format('Y-m-d H:i:s');
$results = $event->calculOccurrence($startDate, $endDate);
return count($results);
}

I use it in a scenario run every day early morning ;

More concretly, i request the event "Present" (calendar_event id 76) in the following calendar:

For instance, the expected behavior is:
on April 09 morning, calculOccurence() for this calendar event "Present" on the next day (april 10) should return 0
on April 10 morning, calculOccurence() for this calendar event "Present" on the next day (april 11) should return >0 and i will take appropriate actions to prepare my coming back home.

Note: i dont know if there is an impact: i use extensively calendar inheritance by inclusion and exclusion of other calendars, so the recursive nature of calculOccurence() is important
Here is a definition of the calendar_event "Present"

I'm aware of the "somewhat" heavy calculation involved in using calculOccurence() this way ; i use it only once a day, very early when the system is quite idle.

I must also stress that i'm not at all a php expert, so please modify my PR if my code does not match the requested quality - not a problem for me to be corrected.