[DOCS]: Airflow DAG Conceptual Documentation and Diagrams

[brettpalmberg]

• [ ] Produce high-level documentation describing the purpose of each Airflow DAG that interacts with the water-api.
• [ ] Develop a conceptual diagram that shows datasources (USGS API, CWMS Radar API, water-api, etc) and the DAGs that retrieve information.

These items should live somewhere in the docsify site in https://github.com/USACE/water

[adamscarberry]

We should consider documentation for airflow dags as an "airflow documentation site/system". This would allow us to standardize the docs for dags and have them available to link to from another service (such as water, cumulus, etc).

Thinking about storing the dag documentation in separate markdown file for each dag that might allow for static site generation from all markdown files.

Not completely thought out yet.

Airflow dag can load the related markdown file to continue to display the documentation within the Airflow UI.