Making OAuth 2.0 auth code flows work between containers and their host OS

The example here relates to using the jl CLI, the command line tool for Joule Studio. Unless otherwise stated, activities described here all happen in the container. Starting the authentication flow To use jl in a project, we need to first authenticate with a Joule Studio backend, using jl login, specifying the sign-in URL obtained from our Joule Studio "Develop > Authorizations" settings: Here's what it looks like when jl login <url> is invoked (details elided for obvious security reasons, and lines split for readability): ; jl login "https://api.eu12.studio.joule.cloud.sap/cli/v1?appTid=bafe9663-... &issuerUrl=https%3A%2F%2Fagy....accounts400.ondemand.com &clientId=ad445849-..." Opening browser to log in to https://agy....accounts400.ondemand.com ... If the browser does not open, copy the URL below and open it manually. https://agy....accounts400.ondemand.com/oauth2/authorize ?response_type=code &client_id=ad445849-... &redirect_uri=http%3A%2F%2F127.0.0.1%3A43963%2Fcallback…