Fixed HttpUri parsing of domain names with underscores.

src/NzbDrone.Common.Test/Http/HttpUriFixture.cs

@@ -7,6 +7,13 @@ namespace NzbDrone.Common.Test.Http
 {
     public class HttpUriFixture : TestBase
     {
+        [TestCase("abc://my_host.com:8080/root/api/")]
+        public void should_parse(string uri)
+        {
+            var newUri = new HttpUri(uri);
+            newUri.FullUri.Should().Be(uri);
+        }
+
         [TestCase("", "", "")]
         [TestCase("/", "", "/")]
         [TestCase("base", "", "base")]

src/NzbDrone.Common/Http/HttpUri.cs

@@ -8,7 +8,7 @@ namespace NzbDrone.Common.Http
 {
     public class HttpUri : IEquatable<HttpUri>
     {
-        private static readonly Regex RegexUri = new Regex(@"^(?:(?<scheme>[a-z]+):)?(?://(?<host>[-A-Z0-9.]+)(?::(?<port>[0-9]{1,5}))?)?(?<path>(?:(?:(?<=^)|/)[^/?#\r\n]+)+/?|/)?(?:\?(?<query>[^#\r\n]*))?(?:\#(?<fragment>.*))?$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
+        private static readonly Regex RegexUri = new Regex(@"^(?:(?<scheme>[a-z]+):)?(?://(?<host>[-_A-Z0-9.]+)(?::(?<port>[0-9]{1,5}))?)?(?<path>(?:(?:(?<=^)|/)[^/?#\r\n]+)+/?|/)?(?:\?(?<query>[^#\r\n]*))?(?:\#(?<fragment>.*))?$", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 
         private readonly string _uri;
         public string FullUri => _uri;