Fix audience validation issues

internal/util/version.go

@@ -0,0 +1,25 @@
+package util
+
+import (
+	"time"
+
+	"github.com/wso2/open-mcp-auth-proxy/internal/constants"
+)
+
+// This function checks if the given version date is after the spec cutover date
+func IsLatestSpec(versionDate time.Time, err error) bool {
+	return err == nil && !versionDate.Before(constants.SpecCutoverDate)
+}
+
+// This function parses a version string into a time.Time
+func ParseVersionDate(version string) (time.Time, error) {
+	return time.Parse("2006-01-02", version)
+}
+
+// This function returns the version string, using the cutover date if empty
+func GetVersionWithDefault(version string) string {
+	if version == "" {
+		return constants.SpecCutoverDate.Format("2006-01-02")
+	}
+	return version
+}