router: support prefix wildcards in virtual hosts domains (#6303)

Adds prefix wildcard support (foo.*) in virtual host domains

Risk Level: Low (does not change current behavior)
Testing: Unit tests
Docs Changes: updated domains field documentation in proto file
Release Notes: updated

Fixes #1269

Signed-off-by: Bartosz Borkowski <bartebor@wp.pl>

Mirrored from https://github.com/envoyproxy/envoy @ af7c845fc5e37ce5b271e1a7b4566f2d1e8ec290

envoy/api/v2/route/route.proto

@@ -39,17 +39,21 @@ message VirtualHost {
   string name = 1 [(validate.rules).string.min_bytes = 1];
 
   // A list of domains (host/authority header) that will be matched to this
-  // virtual host. Wildcard hosts are supported in the form of ``*.foo.com`` or
-  // ``*-bar.foo.com``.
+  // virtual host. Wildcard hosts are supported in the suffix or prefix form.
+  //
+  // Domain search order:
+  //  1. Exact domain names: ``www.foo.com``.
+  //  2. Suffix domain wildcards: ``*.foo.com`` or ``*-bar.foo.com``.
+  //  3. Prefix domain wildcards: ``foo.*`` or ``foo-*``.
+  //  4. Special wildcard ``*`` matching any domain.
   //
   // .. note::
   //
   //   The wildcard will not match the empty string.
   //   e.g. ``*-bar.foo.com`` will match ``baz-bar.foo.com`` but not ``-bar.foo.com``.
-  //   Additionally, a special entry ``*`` is allowed which will match any
-  //   host/authority header. Only a single virtual host in the entire route
-  //   configuration can match on ``*``. A domain must be unique across all virtual
-  //   hosts or the config will fail to load.
+  //   The longest wildcards match first.
+  //   Only a single virtual host in the entire route configuration can match on ``*``. A domain
+  //   must be unique across all virtual hosts or the config will fail to load.
   repeated string domains = 2 [(validate.rules).repeated .min_items = 1];
 
   // The list of routes that will be matched, in order, for incoming requests.