The idea here is to provide an api endpoint to be able to make arbitrary http requests (GET and POST preferably) that will be executed through Hydrus and be able to use the cookies and headers set up in the client for whatever domain.

One use of this for me would be saucenao lookups in Hydrus Web. Since saucenao doesn't have CORS headers Hydrus Web can't directly access their API so the idea would be to put your saucenao api key in the headers settings in Hydrus and then Hydrus Web could make requests to saucenao through the Hydrus API which would bypass the need for CORS and automatically have the right header.