On remote management form the fields username, password and proxy_url are close to each other, it is easy for the user to misunderstand that this password and username refers to the proxy, where it is not.

username and password are used to authenticate to the remote repository.

The proxy password must be provided as part of the URL e.g: user:pass@ip:port

The Serializers includes the help_text that can be used on the UI.

Suggestion is to move proxy_url to the end of the form make it clear that it has nothing to do with username and password, and also include the help_text.