Here is the generated API for "Data Sources"

https://github.com/Azure/azure-sdk-for-python/blob/master/sdk/search/azure-search-documents/azure/search/documents/_service/_generated/operations/_data_sources_operations.py

It is basically CRUD, similar to Synonym Maps.

TBH I am not sure where the REST API is, I don't see it anywhere here:

https://docs.microsoft.com/en-us/rest/api/searchservice/