Add support for FilterMaintenanceAccessory

[#124](#124)

Author: gjvanderheiden

src/main/java/io/github/hapjava/accessories/AirPurifierAccessory.java

@@ -79,23 +79,8 @@ public interface AirPurifierAccessory extends HomekitAccessory {
   /** Unsubscribes from changes in the target state of the air purifier. */
   void unsubscribeTargetState();
 
-  /**
-   * If a filter maintenance service is needed as a linked service to this AirPurifier, this is the
-   * place.
-   *
-   * @return an instance of FilterMaintenanceAccessory, null if not needed.
-   */
-  default FilterMaintenanceAccessory getFilterMaintenanceAccessory() {
-    return null;
-  };
-
   @Override
   default Collection<Service> getServices() {
-    AirPurifierService service = new AirPurifierService(this);
-    FilterMaintenanceAccessory fmAccessory = this.getFilterMaintenanceAccessory();
-    if (fmAccessory != null) {
-      service.addLinkedService(fmAccessory.getPrimaryService());
-    }
-    return Collections.singleton(service);
+    return Collections.singleton(new AirPurifierService(this));
   }
 }