Support arbitrary class KG extraction with unstructured2graph

[Josipmrden]

Is it possible to pre-define the classes in order to generate a specific KG?

[gitbuda]

Keep in mind that this is the same / almost the same as one of the use-cases under https://github.com/memgraph/schema?tab=readme-ov-file#use-cases -> "the classes" should probably be defined there and used under the ai-toolkit, lab, ...