[FEAT] Make NoData value of downloaded tiff available to python api

[SlowMo24]

What is the problem? Please describe.

In our workflow, we execute an eval_script via a SentinelHubRequest to calculate the NDVI. We then run get_data on that request to retrieve the NDVI data array.

By default the value -999 is used as NoDataValue but this is not clear without trying and we could not find a way to retrieve that value programmatically.

Here's the solution

Return a Numpy Masked Array in the get_data method that can hold that information.

Alternatives

Provide a function to retrieve the NoDataValue.

Additional context

We now set the NoDataValue explicitly in the eval_script and keep a constant in our code that represents that value. If one needed flexibility here, she would probably have to do string-replacement when reading in the JS eval_script because the interaction between python and JS is difficult.