Add BE validator

internal/validator/validator.go

@@ -0,0 +1,25 @@
+package validator
+
+type Validator struct {
+	Errors map[string]string
+}
+
+func New() *Validator {
+	return &Validator{Errors: make(map[string]string)}
+}
+
+func (v *Validator) Valid() bool {
+	return len(v.Errors) == 0
+}
+
+func (v *Validator) AddError(key, message string) {
+	if _, exists := v.Errors[key]; !exists {
+		v.Errors[key] = message
+	}
+}
+
+func (v *Validator) Check(ok bool, key, message string) {
+	if !ok {
+		v.AddError(key, message)
+	}
+}