tap-schema architecture and notes

The TAP schema may vary by environment, depending on the tables and data available in that environment. This is controlled by the build-all script in the lsst/sdm_schemas repository.

Each variation of the schema is represented by a different Docker image, which is a MySQL server with the appropriate data preloaded. Whenever a new version of lsst/sdm_schemas is tagged, GitHub Actions builds and pushes all of those Docker images.

Each Science Platform environment then selects the schema to deploy by configuring which Docker image to use in its values-<environment>.yaml file.