Uri.Authority.toString renders leading double slash

[jrudolph]

While the overall rendering of URIs is fine, Uri.Authority.toString will render leading double slashes (which will also fail the round-trip Uri.Authority.parse(authority.toString)):

scala> Uri("http://localhost/test").authority
res1: akka.http.scaladsl.model.Uri.Authority = //localhost

scala> Uri.Authority.parse(res1.toString)
akka.http.scaladsl.model.IllegalUriException: Illegal authority: Invalid input '/', expected authority or 'EOI' (line 1, column 1): //localhost
^
  at akka.http.scaladsl.model.IllegalUriException$.apply(ErrorInfo.scala:40)
  at akka.http.scaladsl.model.Uri$.fail(Uri.scala:750)
  at akka.http.impl.model.parser.UriParser.fail(UriParser.scala:77)
  at akka.http.impl.model.parser.UriParser.parseAuthority(UriParser.scala:72)
  at akka.http.scaladsl.model.Uri$Authority$.parse(Uri.scala:331)
  ... 42 elided

This doesn't seem to be covered by the spec.

https://tools.ietf.org/html/rfc3986#section-3:

   The generic URI syntax consists of a hierarchical sequence of
   components referred to as the scheme, authority, path, query, and
   fragment.

      URI         = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

      hier-part   = "//" authority path-abempty / [...]

  [...]

   The following are two example URIs and their component parts:

         foo://example.com:8042/over/there?name=ferret#nose
         \_/   \______________/\_________/ \_________/ \__/
          |           |            |            |        |
       scheme     authority       path        query   fragment
          |   _____________________|__
         / \ /                        \
         urn:example:animal:ferret:nose

So, the double slashes belong to the hier-part and not to the authority.

In URI we could move the rendering of the double slashes from renderAuthority (which is used in Authority.toString) to renderUriWithoutFragment. Hopefully making this change won't lead to much breakage.

[ktoso]

Be sure to note this issue in the release notes