I am attempting to create a web app (ruby on rails) that requires access to a user's Salesforce environment to perform some REST api calls (SOQL queries) and in doing so I've implemented the web server flow. On a dev org I have access to I have created a connected app and am able to successfully connect to that connected app, authorize against it with a user from that environment and then with the returned authorization code I'm able request an access token and make REST calls. However my goal is to allow a salesforce user to authorize access to their org without having a connected app installed in their environment? How is this done?
To look at this same issue from a different perspective, how does a website such as permcomparator or orgdoctor allow a salesforce user to authorize access to their environment?