Analyse and continue refactoring of the model based on further considerations

[lcomet]

There are additional considerations to take into account, as documented in https://github.com/International-Data-Spaces-Association/ODRL-profile-for-IDS/issues?q=is%3Aissue
Furthermore, the change mentioned in #601 regarding the ids:contractOffer must be considered. In line, the comment from @besteves4 is the following: "Instead of ids:contractOffer, you could stick with plain ODRL and model the policy as an odrl:Offer and use odrl:contractingParty and odrl:contractedParty to express the party who is offering the contract and the party who is being contracted, respectively.
odrl:hasPolicy can be used to connect resources with policies."