Custom Graph Deprecation

[drwelby]

RDA will phase out custom graphs after by the end of 2019. This means the only way to interact with RDA will be to use templates.

In the next release gbdxtools will switch all image objects to use their own templates. Custom graph creation will still work but will throw deprecation warnings.

The initial PR for the change is in #713

Any code that uses gbdxtools to build custom graph objects will have to translate the graph to a template.

Before the EOL of the graph API gbdxtools will remove the custom graph code completely.

If any users rely on custom graph creation and have concerns about not being able to convert to a template, please comment below.

Custom graphs generally are used in this pattern to create custom image objects:

class DRAImage(RDAImage):
    def __new__(cls, cat_id, **kwargs): 
        strip = rda.DigitalGlobeStrip(catId=cat_id, CRS="EPSG:4326", GSD="", 
                                      correctionType="DN", bands='MS', fallbackToTOA=True)
        dra = rda.RadiometricDRA(strip)
        rgb = rda.SmartBandSelect(dra, bandSelection="RGB")        
        self = super(DRAImage, cls).__new__(cls, rgb)
        self.cat_id = cat_id        
        return self

Pre-switchover tasks:

[ ] Add deprecation warnings to gbdxtools
[ ] Hunt down any projects in GitHub that use RDAImage
[ ] Post warnings to internal and external Slack Channels
[ ] Note deprecation in gbdxtools docs and GBDX University where appropriate
[ ] Make a notebook showing conversion of a custom graph to a template and how to use the template in gbdxtools.