Draft: populating test database in workflow_db container

A shell script adds tables to the instance of the archive DB in the db container and imports into them selected data from ssstestdb. (These data files are generated by a script that may be called from the main script; this needs be done only once, then when additional test data are needed.) The test demonstrates that the tables have been loaded properly.

This PR is likely to break the CI pipeline. I just want to see where and how things go south, and if (as I expect) I'm unable to fix the issues, I'll close the PR.