Handle terraform report

Goal

Add support for the new plan report from #207526 (closed) to the gitlab rails project.

Definition of Done

• Work with whoever works on #207526 (closed) to come up with a file format
• Gitlab rails supports the terraform key under artifacts:reports
• Report information is stored the same way other artifact reports are stored
• Update gitlab ci yml documentation with the new report key

Notes

This should be able to be worked on at the same time as #207526 (closed), but the two people working on them should interface to make sure they're on the same page for a document format.