Parameterize database path and deletion

[thekaveman]

Background

Currently, the bin/init.sh script deletes and then recreates (via Django's manage.py helpers) the Sqlite database file every time it is called. This happens both during local development and in the Azure app service -- bin/init.sh is called during the app image's startup.

The Django app settings put the Sqlite database file in the same directory as the source code within the running app (or dev) container. In the Azure app service, this is an ephemeral directory that is lost on app service restarts / redeploys, so it is "good" that the database file is recreated each app service restart.

However, our "data" is encoded in a large data migration file that can read from the environment. We want to move away from configuring the app as code, and the first step is being able to maintain our database file between app service restarts.

Acceptance Criteria

• database is deleted if environment variable e.g. DATABASE_RESET if set and true
• database stored in a location determined by an environment variable e.g. DATABASE_DIR; default to the current directory to maintain existing behavior if unset
• local devcontainer workflow is unaffected / still works OOTB
• DATABASE_DIR set to /home/site/wwwroot for Azure app service; Maintain Sqlite config database in mounted storage container #1673 (comment) Reverted to . for more research
• DATABASE_RESET set to true for Azure app service for now to maintain existing behavior while we migrate to an Admin interface

Additional context

• Research persistent storage options in Azure #1312
• Maintain Sqlite config database in mounted storage container #1673