Investigate Proxy OAI-PMH to add Set to query string

[bootsa]

As

• OKMaps currently can't filter by OAI Set (#32) (e.g. Zenodo Community)

and

• if it's not possible to register a provider as an existing endpoint with a specific Set parameter (#54)

then

• is it possible to produce a proxy endpoint that responds to a BASE call by taking the OAI query (1) and appending a Set parameter to the query string which is passed on to another OAI-PMH endpoint (2) and passing the response back to BASE (3 & 4)?

[bootsa]

Did some initial prodding around with Node and Express with two potential solutions.

• Directly with a normal route and callback - got server to fetch a response from the upstream OAI-PMH endpoint successfully but relaying the response from the proxy back to the client returned a 500 server error - possibly something to do with inconsistent Headers, CORS or mal-formed/incomplete response (looks like it returns a stream object)
• Using the http-proxy middleware library - initial set up fine but not sure how to manipulate the query...

Looks promising but needs further investigation. As it's a more brittle solution than providing a more traditional OAI-PMH endpoint using the simple file server solution (#52) will prioritise that first.