Fix ScheduledEventManagerImpl::setStatus

[raul1ro]

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Changes

• Internal code
• Library interface (affecting end-user code)
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Closes Issue: NaN

Description

The check status != ScheduledEvent.Status.SCHEDULED && getScheduledEvent().getStatus() != ScheduledEvent.Status.ACTIVE is not correct.
According to Discord documentation you can set ACTIVE to COMPLETED, but if the event was ACTIVE, the check was always false and throwing error.

New checks:

• Current status should be different than COMPLETED or CANCELED
• If current status is SCHEDULED, the new one can be only ACTIVE or CANCELED
• If current status is ACTIVE, the new one can be only COMPLETED

I also updated the first check which verifies the new status to not be UNKNOWN.
I added the condition that the new status to not be SCHEDULED too.