Create Postgres superuser password randomly in security mode

[lindseysimple]

🚀 Feature Request

Relevant Package [REQUIRED]

This feature request is for all EdgeX using Postgres database in security mode.

Description [REQUIRED]

Currently the superuser password for Postgres is defined directly in the docker compose file by the POSTGRES_PASSWORD environment variable.

For security concern, the superuser password should not be exposed in the compose file and should be saved in the secret store.

Describe the solution you'd like

A superuser password for Postgres will be generated randomly by the secretstore-setup service if the database is initialized for the first time and will be saved to the secret store; otherwise, the superuser password for Postgres will be retrieved from the secret store.