Improve integration testing

[retrodaredevil]

We use the docker compose gradle plugin to spin up a CouchDB instance. We currently hard code the port as 5984, which is usually fine.

However, to improve this, we should copy how it's being done here: https://github.com/retrodaredevil/couchdb-java/blob/master/couchdb/src/test/java/me/retrodaredevil/couchdbjava/integration/DatabaseService.java

We have environment variables available to us to get the actual address we can refer to it on.