Auth Wrapper (#1174)

* Auth Wrapper

* Tweak cmd flag

* auth_excludes => auth_exclude

* Make Auth.Excludes variadic

* Use metadata.Get (passes through http and http2 it will go through various case formats)

* fix auth wrapper auth.Auth interface initialisation

Co-authored-by: Asim Aslam <asim@aslam.me>

auth/default.go

@@ -18,6 +18,11 @@ func (a *noop) Init(...Option) error {
 	return nil
 }
 
+// Options set in init
+func (a *noop) Options() Options {
+	return a.options
+}
+
 // Generate a new auth Account
 func (a *noop) Generate(id string, ops ...GenerateOption) (*Account, error) {
 	return nil, nil