feature: Add --resolution option to flexmeasures show chart

[victorgarcia98]

vl-convert library, which is used to render the Vega-Lite chart specs uses a embedded node engine which has a very low memory limit. So far, this is not possible not change. The memory limit is hit for large periods of data but we can downsample the data to a coarser resolution to reduce the memory usage.

How to test?

Asset Chart

flexmeasures show chart --start 2023-01-01T00:00:00+01:00 --end 2023-01-10T00:00:00+01:00 --asset 2387  --resolution P1D

Sensor Chart

flexmeasures show chart --start 2023-01-01T00:00:00+01:00 --end 2023-01-10T00:00:00+01:00 --sensor 16860  --resolution P1D

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• 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