create constants for error messages and keys in handlers package

handlers/handlers.go

@@ -0,0 +1,36 @@
+package handlers
+
+const (
+	InvalidRequest  string = "invalid_request"
+	InternalError   string = "internal_error"
+	RequestID       string = "request_id"
+	NotFound        string = "not_found"
+	Created         string = "created"
+	Updated         string = "updated"
+	Deleted         string = "deleted"
+	Enabled         string = "enabled"
+	Disabled        string = "disabled"
+	Retrieved       string = "retrieved"
+	ErrorCreating   string = "error_creating"
+	ErrorUpdating   string = "error_updating"
+	ErrorEnabling   string = "error_enabling"
+	ErrorDisabling  string = "error_disabling"
+	ErrorGetting    string = "error_getting"
+	ErrorGettingAll string = "error_getting_all"
+	InvalidEntityID string = "invalid_entity_id"
+	NotImplemented  string = "not_implemented"
+
+	UserUsernameKey       string = "user_username_key"
+	UserEmailKey          string = "user_email_key"
+	UsernameAlReadyExists string = "username_already_exists"
+	EmailAlreadyExists    string = "email_already_exists"
+	IncorrectPassword     string = "incorrect_password"
+	ErrorGeneratingToken  string = "error_generating_token"
+	LoggedIn              string = "logged_in"
+
+	CategoryNameKey       string = "category_name_key"
+	CategoryAlreadyExists string = "category_already_exists"
+
+	ItemsNameKey      string = "items_name_key"
+	NameAlreadyExists string = "name_already_exists"
+)