[Documentation]: Document programmatic submission via Airflow API

[LucaCinquini]

Write a GitBook page that contains instructions and examples on how to submit an SPS job using the Airflow API:

• with the CURL client
• with a Python script
  Use the cwl_dag.py as the example DAG.

Risks: none
Dependencies: none
Tests: none

[rtapella]

I am actually not sure we want to document this.. shouldn't we be pushing every Unity user towards the OGC API? That way they're writing something that can be used across any compliant ADES (e.g. Unity-HySDS, Unity-Airflow, Unity-HECC, etc.)

[LucaCinquini]

My understanding is that the ASIPS users have asked to use the Airflow API...