External policy hooks discussion

[Spablob]

On one hand, allowing onLicenseMinting and onLinkToParents hooks to call external royalty policies could be useful for external royalty policy developers as they could inject their own custom logic on those 2 moments of an IP lifetime.

On the other hand, these hooks if implemented raise security concerns given permissionless hooks would allow calling possibly malicious or benign but vulnerable contracts, which, in turn, poses a risks to users.

The topic is open to discussion.