Doc: Extensibility for indexing

[SteveLasker]

A SCITT instance will have a well known schema for submitting and querying claims, attestations and endorsements. Often, a claim will have some level of associated evidence.
The evidence may be opaque or may need to be indexed. For instance, a specific SCITT instance my know how to index a specific SBOM format. However, a SCITT instance shouldn't block persistence of unknown formats.

This doc will capture how a SCITT instance may opt into indexing a specific format, providing value over the content.

The most obvious scenario is searching for a package within an SBOM.

[OR13]

This seems like it could become very complicated.

I imagine indexing would happen outside the ledger, based on "content aware" policies.

[SteveLasker]

yup, i was thinking something along the sharepoint and windows indexing model. There would be extensibility points for plugins to hook push/post events to index content specific types.
Then, the query language needs a model for dipping into those indexes.