Match against multiple header values

[sagebind]

For my HTTP client I now have the need to assert that repeated headers are being sent or not with the correct values and number of times. For example, I kind of expected the following to work:

let m = mock("GET", "/")
    .match_header("x-header", "some-value1")
    .match_header("x-header", "some-value2")
    .create();

I want to assert that x-header is present twice in the request, one with the value some-value1 and another with the value some-value2. After looking at the source, I now understand that this will never match anything because instead two matchers are created, both expecting all occurrences of x-header to be equal to the respective values. (Incidentally, seems the error diff is a bit bugged in this scenario and points to the wrong header, but I need to poke around that further.)

I don't currently see a way of asserting what I want to assert, though I do see that internally matchers are given all header values as a slice. I guess this is a feature request then for some sort of matcher that contains a list of matchers, but unlike Matcher::AllOf, requires that each matcher in the list matches a header value uniquely exactly once.

I'd be willing to implement this if this sounds like something you'd be willing to accept.