[#84] Detailed report message Gmail

[snarve]

🗣 Description

This PR covers adding the Detailed report message feature for Gmail and also the Group override policy. Gmail policies cannot be controlled at Group level, so no changes there Also, covered in this PR, updates to the rego code to refer to the updated 'FilterEventsOU'

💭 Motivation and context

Closes #84 , #197

🧪 Testing

• Ensure the report results are as expected for Gmail policies
• All unit tests should pass

✅ Pre-approval checklist

• [x] This PR has an informative and human-readable title.
• [x] Changes are limited to a single goal - eschew scope creep!
• [ ] If applicable, All future TODOs are captured in issues, which are referenced in the PR description.
• [x] The relevant issues PR resolves are linked preferably via closing keywords.
• [x] All relevant type-of-change labels have been added.
• [x] I have read and agree to the CONTRIBUTING.md document.
• [x] These code changes follow cisagov code standards.
• [x] All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• [x] Tests have been added and/or modified to cover the changes in this PR.
• [x] All new and existing tests pass.

✅ Pre-merge Checklist

• [x] This PR has been smoke tested to ensure main is in a functional state when this PR is merged.
• [x] Squash all commits into one PR level commit using the Squash and merge button.

✅ Post-merge Checklist

• [ ] Delete the branch to clean up.
• [ ] Close issues resolved by this PR if the closing keywords did not activate.