Quote password in the PostgreSQL string

[pt-cervest]

Hello!

First of all, thanks a lot for providing this awesome lib. Really appreciate it! 🙏🏽

In my recent attempt to deploy the API on k8s, I encountered a Postgres error and the reason being the password containing special characters. A simple fix is to import from urllib.parse import quote and wrap quote(self.postgres_pass) in stac_fastapi/pgstac/stac_fastapi/pgstac/config.py.

I'm happy to make a subsequent PR - if folks here think it's valuable.

Cheers,
Prayag