feat: add user_setting model (#145)

* feat: add `user_setting` model

* chore: add global store

* chore: update settings in web

* chore: update `i18n` example

api/user_setting.go

@@ -0,0 +1,34 @@
+package api
+
+type UserSettingKey string
+
+const (
+	// UserSettingLocaleKey is the key type for user locale
+	UserSettingLocaleKey UserSettingKey = "locale"
+)
+
+// String returns the string format of UserSettingKey type.
+func (key UserSettingKey) String() string {
+	switch key {
+	case UserSettingLocaleKey:
+		return "locale"
+	}
+	return ""
+}
+
+type UserSetting struct {
+	UserID int
+	Key    UserSettingKey `json:"key"`
+	// Value is a JSON string with basic value
+	Value string `json:"value"`
+}
+
+type UserSettingUpsert struct {
+	UserID int
+	Key    UserSettingKey `json:"key"`
+	Value  string         `json:"value"`
+}
+
+type UserSettingFind struct {
+	UserID int
+}