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/auth.go

@@ -11,6 +11,8 @@ type Auth interface {
 	String() string
 	// Init the auth package
 	Init(opts ...Option) error
+	// Options returns the options set
+	Options() Options
 	// Generate a new auth Account
 	Generate(id string, opts ...GenerateOption) (*Account, error)
 	// Revoke an authorization Account