Momo generates a lot of Mongo Errors

[YaniKolev]

Looks like we expect and gracefully handle a Mongo error here: https://github.com/TNG/momo-scheduler/blob/main/src/repository/SchedulesRepository.ts#L57

However, this spams the logs of any responsible DB with errors like MongoServerError: E11000 duplicate key error collection:(...).

There are expected at this place and we do handle them correctly but the behaviour can make people think there's something wrong with the service.

We should investigate if there's a different way to perform this check

[YaniKolev]

If we decide to solve the issue via transactions, we should make it clear what Mongo version we require. I think they might be a v5 version. We should also make sure to clearly communicate what the required actual DB version is.

[weissu42]

Looks like transactions are available since Mongo 4.2: https://www.mongodb.com/docs/v5.0/core/transactions/
(but one must use a replica set)

[weissu42]

MongoSchedule#isActiveSchedule() seems to be unused and should be removed
(SchedulePing uses SchedulesRepository directly)