Small changes - Githubissues

This branch was created to tackle some small tickets that did not take enough work to justify multiple branches. Main work consists of adding cases for attaching object refs, and associated validation warnings.

Tickets encapsulated:

[x] AF-164: Report
- publishing with object references
- validator warning to block publishing without object references
[ ] AF-165: Observed data (in-progress for restricting type of attached object)
- publishing with object references
- validator warning to block publishing without object references remaining task:
  - validator blocking for incorrect attached object type (must be of type observable
[x] AF-167: Autonomous system
- small fix to publish with incorrect type for number
[x] AF-169: Grouping
- publishing with object references
- validator warning to block publishing without object references

center-for-threat-informed-defense / attack-flow

Small changes #88