Fix age gate page to defend against common user error

pkg/controller/account/age_gate.go

@@ -49,7 +49,12 @@ func AgeGate() http.HandlerFunc {
 			}
 
 			// Validate birthdate is at least age 18.
-			if utility.Age(birthdate) < 18 {
+			if utility.Age(birthdate) <= 5 {
+				// Probably an error: seen some users enter current year by mistake, don't instantly ban them.
+				session.FlashError(w, r, "Please enter a valid birthdate. The year you entered (%d) was probably incorrect.", birthdate.Year())
+				templates.Redirect(w, r.URL.Path)
+				return
+			} else if utility.Age(birthdate) < 18 {
 				// Lock their account and notify the admins.
 				fb := &models.Feedback{
 					Intent:    "report",