Maybe switch api to Import holidays

[timo2o1o]

Describe the bug
The api we use to import holidays seems a little broken. We should maybe switch to https://feiertage-api.de/

[Jusdon]

The problem with this provider is that only one year can be sent per request. Unless I have overlooked something. In our case, however, we need two years in the query.

However, one could send two queries with one year each.

[timo2o1o]

The problem with this provider is that only one year can be sent per request. Unless I have overlooked something. In our case, however, we need two years in the query.

However, one could send two queries with one year each.

I would rather do that, than keep having problems querying the API we use now. Another problem with the actual API is that there is no data for years before 2020.