Support OWASP SCVS V2.16 regarding Copyright

Per OWASP SCVS

> **V2.16** Components defined in SBOM have valid copyright statements

https://scvs.owasp.org/scvs/v2-software-bill-of-materials/

### Current Behavior

Dependency-Track shows the Copyright at Component > View Details > Legal > Copyright. However, I cannot define policy on Copyright, such as "Warn: Copyright is not empty"

### Proposed Behavior

I want to be able to define policy on Copyright.

### Checklist

- [x] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/master/CONTRIBUTING.md#filing-issues)
- [x] I have checked the [existing issues](https://github.com/DependencyTrack/dependency-track/issues) for whether this enhancement was already requested