Build me an API authentication proxy (apigee)

See attached figure of proposed solution. So the circumstances are that I have a iOS app (the client) that only can make token request through the basic authentication protocol, and I have a backend system that only supports token request through the Oauth2 protocol with client credentials. So I need to convert a basic authentication token request made by the app, and convert that to a Oauth2 token request. If the credentials are valid in the backend system, then I get a Access token in return. Ideally I would like to just pass the client ID and client secret from the basic authentication request to the oauth2 token request. But I am not entirely sure that is possible. Storing the credentials can be an option, but as mention I would like to go with just passing them through the proxy. So the job in question is to: - Make an API proxy/converter that makes it possible to convert a token request from basic authentication to Oauth2. Ideally this solution should be made in SAP cloud platform, but using apigee is also an option. - Make the solution easy to copy/paste so it is easy to use on multiple backend systems/data sources - Make some fault tolerance or error logging in case of errors/warnings. - Make it testable - Make some documentation on the work conducted