refactor authentication (#1950)

pkg/api/iam/token/issuer.go

@@ -0,0 +1,10 @@
+package token
+
+// Issuer issues token to user, tokens are required to perform mutating requests to resources
+type Issuer interface {
+	// IssueTo issues a token a User, return error if issuing process failed
+	IssueTo(User) (string, error)
+
+	// Verify verifies a token, and return a User if it's a valid token, otherwise return error
+	Verify(string) (User, error)
+}