Add a fixed frequency schedule

[mintdaniel42]

When just adding the frequency to the current time, due to the system load the execution time will shift by a few milliseconds every run. So after a few hundred runs the delay will no longer be f.ex. 5 minutes but 5 minutes and 10 seconds. This is now fixed by always calculating the time remaining

[amanteaux]

Thank you for your contribution!

When using a fixed delay schedule, the shifting of a few milliseconds after each run is expected: https://github.com/Coreoz/Wisp/tree/master?tab=readme-ov-file#basics-schedules

To get around this, the existing solution to have a fixed frequency schedule is to use a cron expression: https://github.com/Coreoz/Wisp?tab=readme-ov-file#cron

I am not against creating a fixed delay schedule implementation though. If you are interested, can you update your PR with:

• Add a new FixedFrequencySchedule implementation
• Unit test only this implementation (no need to make an integration test with the whole scheduler)
• Add a new static method in Schedules to easily use this implementation
• Update the README.md file accordingly

[mintdaniel42]

Done 👍🏼

[amanteaux]

Thank you!! And sorry for the merge delay!

[mintdaniel42]

No worries. I have to thank you for the merge 😃