code: public GenericResponseBuilder<T> entity(T entity) {
      if (hasErrorEntity) {
        throw new IllegalStateException(
            "errorEntity already set. Only one of entity and errorEntity may be set");
      }
      this.body = entity;
      rawBuilder.entity(entity);
      return this;
    }
docs: Sets the response entity body on the builder.
  
  <p>A specific media type can be set using the {@code type(...)} methods.
  
  @param entity the response entity body
  @return this builder
  @see #type(MediaType)
  @see #type(String)