app: add code for macOS and Windows apps under 'app' (#12933)

* app: add code for macOS and Windows apps under 'app'

* app: add readme

* app: windows and linux only for now

* ci: fix ui CI validation

---------

Co-authored-by: jmorganca <jmorganca@gmail.com>

app/format/field.go

@@ -0,0 +1,30 @@
+//go:build windows || darwin
+
+package format
+
+import (
+	"strings"
+	"unicode"
+)
+
+// KebabCase converts a string from camelCase or PascalCase to kebab-case.
+// (e.g. "camelCase" -> "camel-case")
+func KebabCase(str string) string {
+	var result strings.Builder
+
+	for i, char := range str {
+		if i > 0 {
+			prevChar := rune(str[i-1])
+
+			// Add hyphen before uppercase letters
+			if unicode.IsUpper(char) &&
+				(unicode.IsLower(prevChar) || unicode.IsDigit(prevChar) ||
+					(i < len(str)-1 && unicode.IsLower(rune(str[i+1])))) {
+				result.WriteRune('-')
+			}
+		}
+		result.WriteRune(unicode.ToLower(char))
+	}
+
+	return result.String()
+}

app/format/field_test.go

@@ -0,0 +1,34 @@
+//go:build windows || darwin
+
+package format
+
+import "testing"
+
+func TestKebabCase(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"already-kebab-case", "already-kebab-case"},
+		{"simpleCamelCase", "simple-camel-case"},
+		{"PascalCase", "pascal-case"},
+		{"camelCaseWithNumber123", "camel-case-with-number123"},
+		{"APIResponse", "api-response"},
+		{"mixedCASE", "mixed-case"},
+		{"WithACRONYMS", "with-acronyms"},
+		{"ALLCAPS", "allcaps"},
+		{"camelCaseWITHMixedACRONYMS", "camel-case-with-mixed-acronyms"},
+		{"numbers123in456string", "numbers123in456string"},
+		{"5", "5"},
+		{"S", "s"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			result := KebabCase(tt.input)
+			if result != tt.expected {
+				t.Errorf("toKebabCase(%q) = %q, want %q", tt.input, result, tt.expected)
+			}
+		})
+	}
+}