Allow to specify soc-maxima and soc-minima as a range

[Flix6x]

Description

Non-breaking API change to support less verbose ways of setting the same constraint for a given time window.

Look & Feel

{
    "flex-model": {
        "soc-maxima": [
            {
                "value": 50,
                "datetime": "2024-02-05T11:00:00+01:00",
            },
            {
                "value": 51,
                "start": "2024-02-05T12:00:00+01:00",
                "end": "2024-02-05T13:30:00+01:00"
            },
            {
                "value": 52,
                "start": "2024-02-05T15:00:00+01:00",
                "duration": "PT1H"
            },
            {
                "value": 53,
                "duration": "PT15M",
                "end": "2024-02-05T18:30:00+01:00"
            }
        ]
    }
}

How to test

• Still need to check the flexmeasures-client for compatibility.

Further Improvements

• Update V2G documentation page
• Update API notation page [not updated, as it points to the V2G documentation page for examples.]
• Test whether a P1D duration over a DST transition takes into account the sensor's IANA timezone [with 4db562d we now ground the nominal durations to the start or end, and I've added tests for P1M durations. However, I commented out the P1D and P1W test cases, as they require a fundamental fix in isodate.]

Related Items

Closes #898.

---

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on code under GPL or other license that is incompatible with FlexMeasures

[victorgarcia98]

Very nice! 🎆

The only thing is that, perhaps, this should be added to the endpoint docs.