Make PostgreSQL and Redis connection strings configurable

[imanimen]

Ticket(s)

Closes https://github.com/gatewayd-io/gatewayd/issues/563

Description

Configured the docker-compose.yaml, gatewayd_plugins.yaml to read from the the Environment variables for redis and postresql url string

Related PRs

N/A

Development Checklist

• [x] I have added a descriptive title to this PR.
• [ ] I have squashed related commits together.
• [ ] I have rebased my branch on top of the latest main branch.
• [x] I have performed a self-review of my own code.
• [x] I have commented on my code, particularly in hard-to-understand areas.
• [ ] I have added docstring(s) to my code.
• [ ] I have made corresponding changes to the documentation (docs).
• [ ] I have updated docs using make gen-docs command.
• [ ] I have added tests for my changes.
• [x] I have signed all the commits.

Legal Checklist

• [x] I have read the CONTRIBUTING document.
• [x] I have read and understood the Code of Conduct.
• [x] I have read and agreed to the Apache CLA (required).
• [x] I have read and agreed to the LICENSE (required).