Upgrade postgres to 16

[merobi-hub]

Problem

We are still on Postgres 14 but can easily upgrade the required images to 16.

Solution

Upgrade the images in the relevant docker-compose YML files to 16.

One-line summary: upgrade postgres to 16

Checklist

• You've signed-off your work
• Your changes are accompanied by tests (if relevant)
• Your change contains a small diff and is self-contained
• You've updated any relevant documentation (if relevant)
• You've included a one-line summary of your change for the CHANGELOG.md (Depending on the change, this may not be necessary).
• You've versioned your .sql database schema migration according to Flyway's naming convention (if relevant)
• You've included a header in any source code files (if relevant)