GH-5080 Support for using a user provided document loader with HASMAC JSON-LD

GitHub issue resolved: #5080

Briefly describe the changes proposed in this PR:

PR Author Checklist (see the contributor guidelines for more details):

[ ] my pull request is self-contained
[ ] I've added tests for the changes I made
[ ] I've applied code formatting (you can use mvn process-resources to format from the command line)
[ ] I've squashed my commits where necessary
[ ] every commit message starts with the issue number (GH-xxxx) followed by a meaningful description of the change

eclipse-rdf4j / rdf4j