Add build tags for Firebase

payments/payments_dummy.go

@@ -2,12 +2,17 @@
 
 package payments
 
+// Available is a constant used to indicate that Stripe support is available.
+// It can be disabled with the 'nopayments' build tag.
 const Available = false
 
+// SubscriptionStatus is a dummy type
 type SubscriptionStatus string
 
+// PriceRecurringInterval is dummy type
 type PriceRecurringInterval string
 
+// Setup is a dummy type
 func Setup(stripeSecretKey string) {
 	// Nothing to see here
 }