Add content recommendation endpoints based on L2 Distance of the existing embeddings

[vmesel]

Maybe we could add an endpoint that enables users to fetch similar content based on their inquiry. This could possibly add more options for answers on the front-end.

[vmesel]

We changed our algorithm right now to use cosine similarity, but we still need to add this endpoint, so we can let people, based on a certain content, get the K contents and return them into a JSON response.