internal -> storage; split users into an interface

example/server/storage/token.go

@@ -0,0 +1,25 @@
+package storage
+
+import "time"
+
+type Token struct {
+	ID             string
+	ApplicationID  string
+	Subject        string
+	RefreshTokenID string
+	Audience       []string
+	Expiration     time.Time
+	Scopes         []string
+}
+
+type RefreshToken struct {
+	ID            string
+	Token         string
+	AuthTime      time.Time
+	AMR           []string
+	Audience      []string
+	UserID        string
+	ApplicationID string
+	Expiration    time.Time
+	Scopes        []string
+}