Issue/383 385 rename test setup, upgrade to PostgreSQL 18

[hhund]

• Renames test setups to dev setups
• Upgrades integration tests from PostgreSQL 15 to PostgreSQL 18

Warning: The PostgreSQL 18 docker image requires a different mount point, and will create a deeper folder structure:

• PostgreSQL 15: /var/lib/postgresql/data
• PostgreSQL 18: /var/lib/postgresql

Error from the PostgreSQL 18 container startup with the old mount point:

in 18+, these Docker images are configured to store database data in a
format which is compatible with "pg_ctlcluster" (specifically, using
major-version-specific directory names). This better reflects how
PostgreSQL itself works, and how upgrades are to be performed.

See also docker-library/postgres#1259

Counter to that, there appears to be PostgreSQL data in:
/var/lib/postgresql/data (unused mount/volume)

This is usually the result of upgrading the Docker image without
upgrading the underlying database using "pg_upgrade" (which requires both
versions).

The suggested container configuration for 18+ is to place a single mount
at /var/lib/postgresql which will then place PostgreSQL data in a
subdirectory, allowing usage of "pg_upgrade --link" without mount point
boundary issues.

See docker-library/postgres#37 for a (long)
discussion around this process, and suggestions for how to do so.

closes #383
closes #385