Blend app: implement feature flag to read from Data Platform

[katyalmohit]

Pull Request

Description

• This PR adds an option to read forecasts from the Data Platform instead of the database.
• By default, the blend service still reads forecasts from nowcasting_datamodel.
• If we set the environment variable: READ_FROM_DATA_PLATFORM=true, the service will read forecast values from the Data Platform instead.

Fixes: https://github.com/openclimatefix/client-private/issues/158

How Has This Been Tested?

• Added integration tests
• Tested with the development database and data-platform

Checklist:

• My code follows OCF's coding style guidelines
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings

[PavanRaghavendraKulkarni]

LGTM!

[peterdudfield]

Actually could you run this with data-platform 0.21.2, you'll need to update th docker image too

[peterdudfield]

Also did you run it with the dev env and check that the dashboard is shows the forecast properly. Sometimes the probabilistic values were missing

[katyalmohit]

Also did you run it with the dev env and check that the dashboard is shows the forecast properly. Sometimes the probabilistic values were missing

Yeah, sometimes it does that. I will investigate it further.

[peterdudfield]

Investigate why probabilistic values are none sometimes

[peterdudfield]

I ran this locally and it worked. I think the nonn probablistic values are from old runs, and should be delete from the database. I reckon we go ahead and merge this