feat(infra): tipos ConfigError y ConfigValidation + funciones puras Go (validate, merge, dump)

- ConfigError y ConfigValidation como tipos producto con sus .md en types/infra/
- config_validate: validacion con tags required/format/min/max/oneof via reflection
- config_merge: merge no-mutante de map[string]string con precedencia de override
- config_dump: serializacion de structs a map con mascara *** para campos secret
- 17 tests unitarios, todos PASS

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

functions/infra/config_validate_test.go

@@ -0,0 +1,98 @@
+package infra
+
+import (
+	"testing"
+)
+
+func TestConfigValidate(t *testing.T) {
+	t.Run("struct valido retorna IsValid true", func(t *testing.T) {
+		type Cfg struct {
+			Host string `required:"true"`
+			Port int    `required:"true"`
+		}
+		got := ConfigValidate(Cfg{Host: "localhost", Port: 8080})
+		if !got.IsValid {
+			t.Errorf("expected IsValid=true, errors: %v", got.Errors)
+		}
+		if len(got.Errors) != 0 {
+			t.Errorf("expected no errors, got %v", got.Errors)
+		}
+	})
+
+	t.Run("campo required vacio acumula error", func(t *testing.T) {
+		type Cfg struct {
+			Host string `required:"true"`
+			Key  string `required:"true"`
+		}
+		got := ConfigValidate(Cfg{})
+		if got.IsValid {
+			t.Error("expected IsValid=false")
+		}
+		if len(got.Errors) != 2 {
+			t.Errorf("expected 2 errors, got %d: %v", len(got.Errors), got.Errors)
+		}
+		for _, e := range got.Errors {
+			if e.Tag != "required" {
+				t.Errorf("expected tag 'required', got %q", e.Tag)
+			}
+		}
+	})
+
+	t.Run("format email invalido produce error", func(t *testing.T) {
+		type Cfg struct {
+			Email string `format:"email"`
+		}
+		got := ConfigValidate(Cfg{Email: "not-an-email"})
+		if got.IsValid {
+			t.Error("expected IsValid=false")
+		}
+		if len(got.Errors) == 0 || got.Errors[0].Tag != "format" {
+			t.Errorf("expected format error, got %v", got.Errors)
+		}
+	})
+
+	t.Run("format email valido pasa", func(t *testing.T) {
+		type Cfg struct {
+			Email string `format:"email"`
+		}
+		got := ConfigValidate(Cfg{Email: "user@example.com"})
+		if !got.IsValid {
+			t.Errorf("expected IsValid=true, errors: %v", got.Errors)
+		}
+	})
+
+	t.Run("format url invalido produce error", func(t *testing.T) {
+		type Cfg struct {
+			BaseURL string `format:"url"`
+		}
+		got := ConfigValidate(Cfg{BaseURL: "ftp://bad.url"})
+		if got.IsValid {
+			t.Error("expected IsValid=false")
+		}
+		if len(got.Errors) == 0 || got.Errors[0].Tag != "format" {
+			t.Errorf("expected format error, got %v", got.Errors)
+		}
+	})
+
+	t.Run("puntero a struct funciona igual", func(t *testing.T) {
+		type Cfg struct {
+			Name string `required:"true"`
+		}
+		got := ConfigValidate(&Cfg{Name: "test"})
+		if !got.IsValid {
+			t.Errorf("expected IsValid=true, errors: %v", got.Errors)
+		}
+	})
+
+	t.Run("todos los errores acumulados aunque falle el primero", func(t *testing.T) {
+		type Cfg struct {
+			A string `required:"true"`
+			B string `required:"true"`
+			C string `required:"true"`
+		}
+		got := ConfigValidate(Cfg{})
+		if len(got.Errors) != 3 {
+			t.Errorf("expected 3 errors, got %d", len(got.Errors))
+		}
+	})
+}