feat(withdraw):完成公示撤回及审核相关的功能。

exceptions/improper_operate.go

@@ -0,0 +1,19 @@
+package exceptions
+
+import "fmt"
+
+type ImproperOperateError struct {
+	Message   string
+	Arguments []string
+}
+
+func NewImproperOperateError(msg string, arguments ...string) ImproperOperateError {
+	return ImproperOperateError{
+		Message:   msg,
+		Arguments: arguments,
+	}
+}
+
+func (e ImproperOperateError) Error() string {
+	return fmt.Sprintf("Improper Operate, %s", e.Message)
+}