Get the connection credentials for a database component

Read from the running pod's resolved environment at call time, so the container is the source of truth rather than the template. `component` is a compose service running a database.

curl -X GET "https://example.com/api/workspaces/string/apps/string/db/credentials?component=string"

{  "engine": "postgres",  "port": 0,  "user": "string",  "password": "string",  "database": "string"}