Expose the lineage definition file through an endpoint

[Taepper]

LAPIS can already expose the reference genomes and the database config. However, LAPIS currently does not have knowledge of the lineage definition file. Therefore, we decided that SILO should have an endpoint that exposes this file.

SILO endpoint: GET /linageDefinition/{column}

It should check that the column exists and has generateLineageIndex: true
→ SILO should support multiple lineage trees in the future