Feature for domain_source without domain_access

Problem/Motivation

For some projects, we don't need to enable the module domain_access and have only the module domain_source enabled. Unfortunately, no domain paths are then created.

Steps to reproduce

1. Install and enable domain and domain_source module
2. Install and enable domain_path module
3. Create a node, set domain_source to example.com and insert a domain_path for example.com
4. No domain path will be created

Proposed resolution

Add domain_path support for the case of using only the domain_source method.