Add new middleware for x-forwarded-proto header support

[lukaszkorecki]

This follows existing pattern for x-forwarded-for header support - when x-forwarded-proto is detected and contains one of allowed values, it will override :scheme key in the request map.

[weavejester]

Thanks for the commit. There's some minor formatting/style changes that I've added as inline comments. Can you also change the commit message to:

Add middleware for x-forwarded-proto header

This ensures the PR adheres to the contributing guidelines.

[weavejester]

This comment can be omitted; it doesn't provide any information that can't be already discerned.

[weavejester]

I think it would be better in this case to define this as a set/predicate. This separates out validation from coercion.

(def ^:private valid-scheme? #{"http" "https" "ws" "wss"})

And then in forwarded-scheme-request:

(let [forwarded-proto (get-in request [:headers "x-forwarded-proto"])
      scheme          (some-> forwarded-proto str/trim str/lower-case)]
  (if (and scheme (valid-scheme? scheme))
    (assoc request :scheme (keyword scheme))
    request))

[weavejester]

Remove unnecessary newline.

[weavejester]

Wrap at 80 characters:

  "Middleware that changes the :scheme of the request map to the last value
  present in the X-Forwarded-Proto header."

[weavejester]

Wrap at 80 characters:

  "Change the :scheme key of the request map to the last value present in the
  X-Forwarded-Proto header. See: wrap-forwarded-scheme."

[lukaszkorecki]

Happy to help - I'll pick this up on Monday and apply all suggestions. I assume you prefer this PR be a squashed commit, right?

[weavejester]

Yep; this seems a simple enough addition that only one commit is required.