feat(document-search): document-search sources string resolver

[mhordynski]

Feature description

Add a string resolver to identify which sources the user wants to ingest into a document search.

Here’s an example:

await document_search.ingest("gcs://my_bucket/*")  # Include all files from the GCS bucket "my_bucket"
await document_search.ingest("s3://my_bucket/*")  # Include all files from the S3 bucket "my_bucket"

Each Source can register a new "protocol" in the SourceResolver, thus user-defined sources also can be auto-resolved.

Motivation

Currently, users are forced to delve into our documentation to figure out the different sources. Additionally, the Source.list_source API is not streamlined and varies between different implementations.

Additional context

No response