Implementing the Multi-Tenant Virtual Catalogs STAC API Extension

[jonhealy1]

Hi. I have pr open here to implement this extension here: #366

This is presently working as an optional extension in stac-fastapi-elasticsearch-opensearch

Extension spec (STAC API Extension): https://github.com/StacLabs/multi-tenant-catalogs

stac-fastapi extension: https://github.com/StacLabs/stac-fastapi-catalogs-extension