feat: complete API-driven projects with infrastructure and business acceptance

examples/userService/internal/model/errors.go

@@ -0,0 +1,11 @@
+package model
+
+import "errors"
+
+// Domain errors are translated into HTTP responses only by the handler layer.
+var (
+	ErrUserNotFound = errors.New("user not found")
+	ErrEmailTaken   = errors.New("email already in use")
+	ErrInvalidUser  = errors.New("invalid user")
+	ErrInvalidPage  = errors.New("invalid pagination")
+)