[BE] Add an option to run ACUITY with a non-containerized database

Currently, ACUITY only uses a containerized database, and it is definitely not a good solution for production in the time being (but still handy for development). We need to have an option to run it with an external DB (cloud-based or not). To do it:
- the corresponding configs should be updated with external DB URL and credentials
- system should be able to run without the DB container