Make builders final for AbstractSettings implementations

Closes gh-825

oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/settings/ClientSettings.java

@@ -104,7 +104,7 @@ public final class ClientSettings extends AbstractSettings {
 	/**
 	 * A builder for {@link ClientSettings}.
 	 */
-	public static class Builder extends AbstractBuilder<ClientSettings, Builder> {
+	public final static class Builder extends AbstractBuilder<ClientSettings, Builder> {
 
 		private Builder() {
 		}

oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/settings/ProviderSettings.java

@@ -137,7 +137,7 @@ public final class ProviderSettings extends AbstractSettings {
 	/**
 	 * A builder for {@link ProviderSettings}.
 	 */
-	public static class Builder extends AbstractBuilder<ProviderSettings, Builder> {
+	public final static class Builder extends AbstractBuilder<ProviderSettings, Builder> {
 
 		private Builder() {
 		}

oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/settings/TokenSettings.java

@@ -123,7 +123,7 @@ public final class TokenSettings extends AbstractSettings {
 	/**
 	 * A builder for {@link TokenSettings}.
 	 */
-	public static class Builder extends AbstractBuilder<TokenSettings, Builder> {
+	public final static class Builder extends AbstractBuilder<TokenSettings, Builder> {
 
 		private Builder() {
 		}