Support an additional input data source type

[JBurkinshaw]

At present, PostgreSQL/PostGIS is the only supported input data source type.

Based on priorities, determine an alternate input data source and add support for it. This could include a text format like GeoJSON (potentially ndjson or GeoJSON Text Sequences flavors) or something entirely different.

There has also been some discussion around apache parquet and geo-arrow in relation to STAC in the past.

New sources can be added to feapi/app/feapi/app/data/sources. Note that references to feapi are likely to change to oaff in the future. This path will change to oaff/app/oaff/app/data/sources when that happens.