Revert TopshelfExitCode back to enum

src/Topshelf/TopshelfExitCode.cs

@@ -12,37 +12,16 @@
 // specific language governing permissions and limitations under the License.
 namespace Topshelf
 {
-    public struct TopshelfExitCode
-    {
-        private readonly int _exitCode;
-
-        public TopshelfExitCode(int exitCode)
-        {
-            _exitCode = exitCode;
-        }
-
-        public static explicit operator int(TopshelfExitCode topshelfExitCode)
-        {
-            return topshelfExitCode._exitCode;
-        }
-
-        // windows service exit code compliant 
-        // https://docs.microsoft.com/en-us/windows/desktop/Debug/system-error-codes
-        public static TopshelfExitCode Ok { get; } = new TopshelfExitCode(0);
-        public static TopshelfExitCode ServiceAlreadyInstalled { get; } = new TopshelfExitCode(1242);
-        public static TopshelfExitCode ServiceNotInstalled { get; } = new TopshelfExitCode(1243);
-        public static TopshelfExitCode ServiceAlreadyRunning { get; } = new TopshelfExitCode(1056);
-        public static TopshelfExitCode ServiceNotRunning { get; } = new TopshelfExitCode(1062);
-        public static TopshelfExitCode ServiceControlRequestFailed { get; } = new TopshelfExitCode(1064);
-        public static TopshelfExitCode AbnormalExit { get; } = new TopshelfExitCode(1067);
-
-        // non-compliant
-        public static TopshelfExitCode SudoRequired { get; } = new TopshelfExitCode(2);
-        public static TopshelfExitCode NotRunningOnWindows { get; } = new TopshelfExitCode(11);
-
-        public override string ToString()
-        {
-            return $"Exit code: {_exitCode}";
-        }
-    }
-}
+	public enum TopshelfExitCode
+	{
+		Ok = 0,
+		ServiceAlreadyInstalled = 1242,
+		ServiceNotInstalled = 1243,
+		ServiceAlreadyRunning = 1056,
+		ServiceNotRunning = 1062,
+		ServiceControlRequestFailed = 1064,
+		AbnormalExit = 1067,
+		SudoRequired = 2,
+		NotRunningOnWindows = 11
+	}
+}