Dynamic URL or credentials for API Connector

Is there any way to dynamically substitute the URL or credentials (ex. HTTP basic auth) for API Connector calls? In my case the application will be used for different clients and the REST endpoint and credentials will be different across clients.

If you want to do that, you cannot use the Auth from API connector and you need to process the auth in each call. This will let you dynamically fill auth info.
However, if the API offer an oAuth2 login process, this is what you should use.