Add whitelist functionality

- Implement whitelist package for filtering URLs
- Support pattern matching for allowed URLs
- Add URL validation against whitelist patterns
- Include test cases for whitelist functionality

common/whiteList/whitelist.go

@@ -0,0 +1,74 @@
+package whiteList
+
+import (
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+
+	"gemini-grc/config"
+	"gemini-grc/logging"
+	"git.antanst.com/antanst/xerrors"
+)
+
+var whitelist []regexp.Regexp //nolint:gochecknoglobals
+
+func Initialize() error {
+	var err error
+
+	// Initialize whitelist
+	if config.CONFIG.WhitelistPath != "" {
+		if err = loadWhitelist(config.CONFIG.WhitelistPath); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func loadWhitelist(filePath string) error {
+	if whitelist != nil {
+		return nil
+	}
+
+	data, err := os.ReadFile(filePath)
+	if err != nil {
+		whitelist = []regexp.Regexp{}
+		return xerrors.NewError(fmt.Errorf("could not load whitelist file: %w", err), 0, "", true)
+	}
+
+	lines := strings.Split(string(data), "\n")
+	whitelist = []regexp.Regexp{}
+
+	for _, line := range lines {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		regex, err := regexp.Compile(line)
+		if err != nil {
+			return xerrors.NewError(fmt.Errorf("could not compile whitelist line %s: %w", line, err), 0, "", true)
+		}
+		whitelist = append(whitelist, *regex)
+	}
+
+	if len(whitelist) > 0 {
+		logging.LogInfo("Loaded %d whitelist entries", len(whitelist))
+	}
+
+	return nil
+}
+
+func Shutdown() error {
+	return nil
+}
+
+// IsWhitelisted checks if the URL matches any whitelist pattern
+func IsWhitelisted(u string) bool {
+	for _, v := range whitelist {
+		if v.MatchString(u) {
+			return true
+		}
+	}
+	return false
+}