Schedule pipeline so database fixture errors in gitlab are automatically detected

Problem

The seed phase of GDK installs is currently a significant pain point. As noted in #594 (closed) and elsewhere, if the seed phase fails you can't simply re-run the installation – you need to take special action with the database. And at it seems (at least recently) failures in the seed phase have been unusually frequent.

Proposal

One idea to reduce failures in the seed stage is to add test coverage. As @alexkalderimis pointed out elsewhere, simple RSpec tests might not be sufficient and "A better approach is probably to have a CI job that replicates the GDK [install] process, and cause things to fail at the CI level." Is that a viable way to safeguard against failures in the seed phase of GDK installs? But GDK already has test coverage for the install process.

The tricky part is running the tests whenever there are changes to gitlab migrations. It seems the simplest solution for automatically identifying unnoticed bugs in gitlab is to schedule the GDK pipeline to run hourly/daily.

EDIT 2019-09-18: Changed title and proposal.