RemoteUserMiddleware needs a get_username method

[Adrien Kunysz]

As currently implemented, the only way to customise how RemoteUserMiddleware gets the username is through the "header" variable. This is then used in call and acall methods like this:

            username = request.META[self.header]

It would be convenient to move that logic into a separate method that could be overridden. For example:

get_username(self):
    return request.META[self.header]    

Specific use case: the proxy I have in front of Django always sets two specific headers (say "X-Username" and "X-Authenticated"). The value of "X-Username" is only valid if "X-Authenticated" is "true", otherwise it should be ignored (typically it ends up being a single space character). I use PersistentRemoteMiddleware to use X-Username but the only way I found to ignore it when X-Authenticated is not true is to override call / acall or clean_username. Both seem rather fragile while a small change to RemoteUserMiddleware would make for a much more robust, flexible and maintainable solution.

With the proposed change, in my child class I could just say

def get_username(self):
    if request.META["X-Authenticated"].lower() != "true":
        raise KeyError
    else:
        return request.META[self.header]

I am happy to propose a patch if we can agree this change is desirable.