Cleanup builders

Author: SgtSilvio

src/main/java/com/hivemq/mqtt/client2/internal/MqttRxClientBuilder.java

@@ -90,7 +90,7 @@ public MqttRxClientBuilder() {}
     }
 
     @Override
-    public @NotNull MqttRxClientBuilder advancedConfig(final @NotNull Mqtt5AdvancedConfig advancedConfig) {
+    public @NotNull MqttRxClientBuilder advancedConfig(final @Nullable Mqtt5AdvancedConfig advancedConfig) {
         this.advancedConfig = Checks.notImplemented(advancedConfig, MqttAdvancedConfig.class, "Advanced config");
         return this;
     }

src/main/java/com/hivemq/mqtt/client2/internal/message/connect/MqttConnectRestrictionsBuilder.java

@@ -125,6 +125,8 @@ public Default() {}
     public static class Nested<P> extends MqttConnectRestrictionsBuilder<Nested<P>>
             implements Mqtt5ConnectRestrictionsBuilder.Nested<P>, Mqtt3ConnectRestrictionsBuilder.Nested<P> {
 
+        private final @NotNull Function<? super MqttConnectRestrictions, P> parentConsumer;
+
         public Nested(
                 final @NotNull MqttConnectRestrictions restrictions,
                 final @NotNull Function<? super MqttConnectRestrictions, P> parentConsumer) {
@@ -133,8 +135,6 @@ public Nested(
             this.parentConsumer = parentConsumer;
         }
 
-        private final @NotNull Function<? super MqttConnectRestrictions, P> parentConsumer;
-
         @Override
         @NotNull Nested<P> self() {
             return this;

src/main/java/com/hivemq/mqtt/client2/internal/mqtt3/Mqtt3RxClientViewBuilder.java

@@ -77,6 +77,11 @@ public Mqtt3RxClientViewBuilder(
         }
     }
 
+    @Override
+    protected @NotNull Mqtt3RxClientViewBuilder self() {
+        return this;
+    }
+
     private @NotNull MqttConnectedListener<MqttConnectedContextImpl> wrapConnectedListener(
             final @NotNull MqttConnectedListener<? super Mqtt3ConnectedContextView> delegate) {
         return context -> delegate.onConnected(new Mqtt3ConnectedContextView(context));
@@ -129,11 +134,6 @@ public Mqtt3RxClientViewBuilder(
         return new Mqtt3PublishViewBuilder.WillNested<>(this::willPublish);
     }
 
-    @Override
-    protected @NotNull Mqtt3RxClientViewBuilder self() {
-        return this;
-    }
-
     @Override
     public @NotNull Mqtt3RxClientView build() {
         return buildRx();