Add logic to construct connection string or params

[AlanCoding]

Currently, this library expects the user to provide a valid set of kwargs to pass directly to the psycopg library connect method, or any of the connection classes (all the same anyway).

However, the dispatcher should adopt the logic that AWX has to do this. This requires having the Django and psycopg dependencies installed, so it would be pg_notify specific.

This logic exists in:

https://github.com/ansible/awx/blob/devel/awx/main/dispatch/__init__.py

The idea is that we would get the listener connection info from Django settings values, DATABASES and LISTENER_DATABASES, and that the dispatcher library would standardize this practice. This is another argument for having a small Django test app to test against.

[AlanCoding]

Related to ansible/awx#15736

[AlanCoding]

Related to ansible/django-ansible-base#686