Enhancement: Empty config

When user starts kportal for the first time, and there is no config file,
kportal should create an empty config file with default values and empty
forwarding rules, so that user can easily edit the config file and add their
own rules.

internal/config/config_test.go

@@ -97,7 +97,7 @@ func TestLoadConfig_FileNotFound(t *testing.T) {
 	cfg, err := LoadConfig("/non/existent/path/.kportal.yaml")
 	assert.Error(t, err, "LoadConfig should fail with non-existent file")
 	assert.Nil(t, cfg, "config should be nil on error")
-	assert.Contains(t, err.Error(), "failed to stat config file", "error should mention stat failure")
+	assert.Equal(t, ErrConfigNotFound, err, "should return ErrConfigNotFound")
 }
 
 func TestForward_ID(t *testing.T) {
@@ -397,3 +397,123 @@ func TestHTTPLogSpec_UnmarshalYAML(t *testing.T) {
 		})
 	}
 }
+
+func TestNewEmptyConfig(t *testing.T) {
+	cfg := NewEmptyConfig()
+	assert.NotNil(t, cfg, "NewEmptyConfig should return non-nil config")
+	assert.Empty(t, cfg.Contexts, "NewEmptyConfig should have empty contexts")
+	assert.True(t, cfg.IsEmpty(), "NewEmptyConfig should be considered empty")
+}
+
+func TestConfig_IsEmpty(t *testing.T) {
+	tests := []struct {
+		name     string
+		config   *Config
+		expected bool
+	}{
+		{
+			name:     "nil contexts",
+			config:   &Config{},
+			expected: true,
+		},
+		{
+			name:     "empty contexts slice",
+			config:   &Config{Contexts: []Context{}},
+			expected: true,
+		},
+		{
+			name: "context with empty namespaces",
+			config: &Config{
+				Contexts: []Context{
+					{Name: "test", Namespaces: []Namespace{}},
+				},
+			},
+			expected: true,
+		},
+		{
+			name: "context with namespace but no forwards",
+			config: &Config{
+				Contexts: []Context{
+					{
+						Name: "test",
+						Namespaces: []Namespace{
+							{Name: "default", Forwards: []Forward{}},
+						},
+					},
+				},
+			},
+			expected: true,
+		},
+		{
+			name: "config with forward",
+			config: &Config{
+				Contexts: []Context{
+					{
+						Name: "test",
+						Namespaces: []Namespace{
+							{
+								Name: "default",
+								Forwards: []Forward{
+									{Resource: "pod/app", Port: 8080, LocalPort: 8080},
+								},
+							},
+						},
+					},
+				},
+			},
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, tt.config.IsEmpty())
+		})
+	}
+}
+
+func TestCreateEmptyConfigFile(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, ".kportal.yaml")
+
+	// Create empty config file
+	err := CreateEmptyConfigFile(configPath)
+	assert.NoError(t, err, "CreateEmptyConfigFile should succeed")
+
+	// Verify file exists
+	_, err = os.Stat(configPath)
+	assert.NoError(t, err, "config file should exist")
+
+	// Verify file is readable and parseable
+	cfg, err := LoadConfig(configPath)
+	assert.NoError(t, err, "should be able to load created config")
+	assert.NotNil(t, cfg, "config should not be nil")
+	assert.True(t, cfg.IsEmpty(), "created config should be empty")
+
+	// Verify file permissions (0600)
+	info, _ := os.Stat(configPath)
+	assert.Equal(t, os.FileMode(0600), info.Mode().Perm(), "file should have 0600 permissions")
+
+	// Verify file contains helpful header
+	content, _ := os.ReadFile(configPath)
+	assert.Contains(t, string(content), "# kportal configuration file", "should contain header comment")
+	assert.Contains(t, string(content), "Example forward", "should contain example")
+}
+
+func TestCreateEmptyConfigFile_AlreadyExists(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, ".kportal.yaml")
+
+	// Create existing file
+	err := os.WriteFile(configPath, []byte("existing content"), 0644)
+	assert.NoError(t, err)
+
+	// Try to create config file - should fail
+	err = CreateEmptyConfigFile(configPath)
+	assert.Error(t, err, "CreateEmptyConfigFile should fail when file exists")
+	assert.Contains(t, err.Error(), "already exists")
+
+	// Verify original content is preserved
+	content, _ := os.ReadFile(configPath)
+	assert.Equal(t, "existing content", string(content))
+}