VLM API requivement: Return records associated with all reference builds that lift over to the request

[jsstevenson]

From API doc:

The assemblyId is provided in the request in order to specify a single genomic sequence. However, responses must include counts across all available reference builds available in a given database. It is the responsibility of each API node to handle any liftover required to map a query assembly to their own assembly(s)

Currently an ingested VCF is associated with a build defined at ingest time. When the VCF is loaded, AnyVar does load a lifted-over variant internally as well, and a mapping between them. But AnyVLM's variant counts endpoint doesn't make use of these mappings, and the VRS ID associated with the count is based on whatever you uploaded.

We need to ensure that a response includes all lifted-over equivalents. A few possible ways forward

• Once /variant_counts has a VRS ID, it should ping AnyVar for any liftover mappings matching that ID, and then lookup stored allele counts for the original ID and the mapped ID(s) ( <-- I think this is the way)
• AnyVar could have a way of optionally including mappings in the response to POST /variation so that we don't need to make the same HTTP request twice (nice-to-have upgrade, but maybe makes the response weird)
• At ingest time, AnyVLM could store counts with associations to all liftover-equivalent VRS IDs instead of the requested VRS ID (meh)
• At ingest time, AnyVLM could always associate to the build 38 variant, and always lift over variant requests up to 38 first (meh)