feature request: allow specifying temporal extent with single string

[soxofaan]

Temporal extents have to be specified as a list/tuple with two dates. Often, when experimenting/exploring, you just need a single year or month, it would be handy if you can just pass temporal_extent="2022" or temporal_extent="2023-04", which would be converted automatically by the client to appropriate date ranges

[soxofaan]

PR #461 was merged but I'd like to iterate a bit further on it:

• I don't think that string_to_temporal_extent or even get_temporal_extent should be user-facing helpers (related: #465). They should just be reusable helpers for actual user-facing methods like Connection.load_collection, DataCube.filter_temporal, ... As such I would not document this feature through the doc strings of these functions, but in the rst docs somewhere (e.g. https://open-eo.github.io/openeo-python-client/data_access.html seems like a good option), which could then be linked to from the docs of Connection.load_collection, DataCube.filter_temporal, ... Make sure to mention that year/month based extent handling is available since version 0.23.0
• add some tests of this feature directly with Connection.load_collection, DataCube.filter_temporal
• is usage like cube.filter_temporal("2020", "2022") or load_collection(..., temporal_extent=["2021-03", "2022-04"]) also handled: take first day of start date and last day + 1 for end date?
• Also I think this feature is worth mentioning in the CHANGELOG

[soxofaan]

done now: merged #468