ensure correct redirect uri query handling

[maxcountryman]

This updates the way macros handle the redirect URI such that the query string is handled in a more correct way. Prior to this, the macros assumed no other query. Now we extend the query, if present, with the configured redirect field and URI.

Fixes https://github.com/maxcountryman/axum-login/issues/143.

[maxcountryman]

cc @benwilber: let me know if this addresses your original issue.

[benwilber]

Thank you! I'll test this and report back!

[benwilber]

It works great except in the case where my login_url already has a next= parameter. In that case it is actually adding a second next= which I don't think is the correct behavior. If I add &next=foo here then the resulting URL becomes:

Some("/login?next=%2F&foo=bar&foo=baz&next=foo")

Where the next parameter has now been repeated. It's kind of ambiguous which actual next= parameter will be used in this case. Because axum-login is adding this parameter implicitly, I think a good behavior would be for it to only add it's own next param if the same param is not already present in my login_url, which presumably would have been added intentionally. This could also address a potential issue where a redirect loop keeps adding next= over and over again. I haven't actually seen that issue, but seems plausible.

I love this library! Thanks for making it!

[maxcountryman]

Thanks for spotting that. I agree with your assessment.