refactor: flash messages framework (resolve #446)

models/view/common.go

@@ -0,0 +1,19 @@
+package view
+
+type BasicViewModel interface {
+	SetError(string)
+	SetSuccess(string)
+}
+
+type Messages struct {
+	Success string
+	Error   string
+}
+
+func (m *Messages) SetError(message string) {
+	m.Error = message
+}
+
+func (m *Messages) SetSuccess(message string) {
+	m.Success = message
+}