Docstrings - inline code docs

[clausmichele]

Something that is still missing comparing this repository with the old openeo-processes-python are docstrings, can we consider adding them? Is there a reason why they were not ported over?
It could be also useful to point out the openEO processes version we are targeting in each process implementation.

[LukeWeidenwalker]

No real reason other than the combination of:

• the previous docstrings being outdated in some places and therefore not immediately portable
• not having docs autogenerated with e.g. sphinx, so the utility being somewhat lower
• us just not taking the time to do this properly
  I think this is probably something that wants to be added gradually, feel free to add some when it's convenient.

I'll create an issue to setup docs generation, that's probably a good thing to have at some point.

About the spec version, not entirely sure about that. We could either define a version of openeo that the entire repo targets, or as you propose point it out separately in each process implementation. I feel that one version for all is much less effort for about the same benefit, just because I don't think we'd ever have multiple versions of the same process in this repo. I imagine there's a clever way of versioning/releasing this package to support separate 1.1/1.2/2.0 tracks, but given the maturity of this repo, I don't think this should be a priority anytime soon.