codacy: A class which only has private constructors should be final

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

src/main/java/com/nextcloud/android/sso/Constants.java

@@ -24,7 +24,7 @@
 
 package com.nextcloud.android.sso;
 
-public class Constants {
+public final class Constants {
     // Authenticator related constants
     public static final String SSO_USERNAME = "username";
     public static final String SSO_TOKEN = "token";

src/main/java/com/owncloud/android/authentication/OAuth2Constants.java

@@ -25,8 +25,7 @@ package com.owncloud.android.authentication;
  * 
  * Includes required and optional parameter NAMES used in the 'authorization code' grant type.
  */
-
-public class OAuth2Constants {
+public final class OAuth2Constants {
     /// Parameters to send to the Authorization Endpoint
     public static final String KEY_RESPONSE_TYPE = "response_type";
     public static final String KEY_REDIRECT_URI = "redirect_uri";

src/main/java/com/owncloud/android/utils/MimeType.java

@@ -20,7 +20,7 @@ package com.owncloud.android.utils;
 /**
  * Class containing the mime types.
  */
-public class MimeType {
+public final class MimeType {
     public static final String DIRECTORY = "DIR";
     public static final String JPEG = "image/jpeg";
     public static final String TIFF = "image/tiff";