[FR] - Adding "Threat actor" as a model

[rickenella]

Is your feature request related to a problem? Please describe.
Not really, but potential redundancy

Describe the solution you'd like
Adding the "Threat Actor" to the existing models, which could then be linked to a case.

Describe alternatives you've considered
At the moment, you do this by adding it as a custom attribute to a case, for example.
In this case, however, it would be very redundant to list all the information again each time. On the other hand, a lot of threat intelligence would be lost if this were not done consistently and no other specific referencing structure was used.

The request is similar to an another open issue, but we still see a difference between a Threat Hunting and Threat Actor section.