Add i18n support with English and Spanish translations

- Created i18n package with translator and middleware
- Added translation files for English (en.json) and Spanish (es.json)
- Updated all HTTP handlers to use i18n for error/success messages
- Added comprehensive test coverage for i18n (87%)
- Updated CI workflow to use Go 1.24
- All tests passing with 50.8% total coverage

internal/i18n/i18n_test.go

@@ -0,0 +1,252 @@
+package i18n
+
+import (
+	"testing"
+
+	"golang.org/x/text/language"
+)
+
+func TestNewTranslator(t *testing.T) {
+	translator, err := NewTranslator()
+	if err != nil {
+		t.Fatalf("Failed to create translator: %v", err)
+	}
+
+	if translator == nil {
+		t.Fatal("Expected translator to be non-nil")
+	}
+
+	if translator.translations == nil {
+		t.Fatal("Expected translations map to be initialized")
+	}
+
+	if len(translator.translations) != 2 {
+		t.Errorf("Expected 2 languages, got %d", len(translator.translations))
+	}
+}
+
+func TestGetLanguage(t *testing.T) {
+	translator, _ := NewTranslator()
+
+	tests := []struct {
+		name           string
+		acceptLanguage string
+		expected       language.Tag
+	}{
+		{
+			name:           "English",
+			acceptLanguage: "en-US",
+			expected:       language.English,
+		},
+		{
+			name:           "Spanish",
+			acceptLanguage: "es-ES",
+			expected:       language.Spanish,
+		},
+		{
+			name:           "Empty defaults to English",
+			acceptLanguage: "",
+			expected:       language.English,
+		},
+		{
+			name:           "Unknown language defaults to English",
+			acceptLanguage: "fr-FR",
+			expected:       language.English,
+		},
+		{
+			name:           "Spanish with quality",
+			acceptLanguage: "es-ES,es;q=0.9",
+			expected:       language.Spanish,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := translator.GetLanguage(tt.acceptLanguage)
+			if result != tt.expected {
+				t.Errorf("Expected %v, got %v", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestError(t *testing.T) {
+	translator, _ := NewTranslator()
+
+	tests := []struct {
+		name     string
+		lang     language.Tag
+		key      string
+		expected string
+	}{
+		{
+			name:     "English error message",
+			lang:     language.English,
+			key:      "invalid_request_body",
+			expected: "Invalid request body",
+		},
+		{
+			name:     "Spanish error message",
+			lang:     language.Spanish,
+			key:      "invalid_request_body",
+			expected: "Cuerpo de solicitud inválido",
+		},
+		{
+			name:     "Missing key returns key",
+			lang:     language.English,
+			key:      "non_existent_key",
+			expected: "non_existent_key",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := translator.Error(tt.lang, tt.key)
+			if result != tt.expected {
+				t.Errorf("Expected '%s', got '%s'", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestSuccess(t *testing.T) {
+	translator, _ := NewTranslator()
+
+	tests := []struct {
+		name     string
+		lang     language.Tag
+		key      string
+		expected string
+	}{
+		{
+			name:     "English success message",
+			lang:     language.English,
+			key:      "logged_out",
+			expected: "Successfully logged out",
+		},
+		{
+			name:     "Spanish success message",
+			lang:     language.Spanish,
+			key:      "logged_out",
+			expected: "Sesión cerrada exitosamente",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := translator.Success(tt.lang, tt.key)
+			if result != tt.expected {
+				t.Errorf("Expected '%s', got '%s'", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestValidation(t *testing.T) {
+	translator, _ := NewTranslator()
+
+	tests := []struct {
+		name     string
+		lang     language.Tag
+		key      string
+		expected string
+	}{
+		{
+			name:     "English validation message",
+			lang:     language.English,
+			key:      "email_required",
+			expected: "email is required",
+		},
+		{
+			name:     "Spanish validation message",
+			lang:     language.Spanish,
+			key:      "email_required",
+			expected: "el email es requerido",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := translator.Validation(tt.lang, tt.key)
+			if result != tt.expected {
+				t.Errorf("Expected '%s', got '%s'", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestEmail(t *testing.T) {
+	translator, _ := NewTranslator()
+
+	tests := []struct {
+		name     string
+		lang     language.Tag
+		key      string
+		expected string
+	}{
+		{
+			name:     "English email message",
+			lang:     language.English,
+			key:      "welcome_subject",
+			expected: "Welcome to Apocapoc!",
+		},
+		{
+			name:     "Spanish email message",
+			lang:     language.Spanish,
+			key:      "welcome_subject",
+			expected: "¡Bienvenido a Apocapoc!",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := translator.Email(tt.lang, tt.key)
+			if result != tt.expected {
+				t.Errorf("Expected '%s', got '%s'", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestTranslate(t *testing.T) {
+	translator, _ := NewTranslator()
+
+	tests := []struct {
+		name     string
+		lang     language.Tag
+		category string
+		key      string
+		expected string
+	}{
+		{
+			name:     "Valid category and key",
+			lang:     language.English,
+			category: "errors",
+			key:      "user_not_found",
+			expected: "User not found",
+		},
+		{
+			name:     "Invalid category returns key",
+			lang:     language.English,
+			category: "invalid_category",
+			key:      "some_key",
+			expected: "some_key",
+		},
+		{
+			name:     "Unsupported language fallback to English",
+			lang:     language.French,
+			category: "errors",
+			key:      "user_not_found",
+			expected: "User not found",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := translator.Translate(tt.lang, tt.category, tt.key)
+			if result != tt.expected {
+				t.Errorf("Expected '%s', got '%s'", tt.expected, result)
+			}
+		})
+	}
+}