[REQ][JAVA] Feature Request Description

Is your feature request related to a problem? Please describe.

Using the java generator, with okhttp-gson (the default), the model classes raise exceptions whenever the API returns a property the models do not know about. It does not seem that (at least) some of the other library generators share this problem, only based on my own brief inspection of the resulting code

Describe the solution you'd like

I would like for the models to tolerate properties that weren't known at the time of generation

Describe alternatives you've considered

Vending my own template, okhttp-gson/pojo.mustache

Additional context

The code I wish to remove looks like this:

  public static void validateJsonElement(JsonElement jsonElement) throws IOException {
      // ...
      
      Set<Map.Entry<String, JsonElement>> entries = jsonElement.getAsJsonObject().entrySet();
      // check to see if the JSON string contains additional fields
      for (Map.Entry<String, JsonElement> entry : entries) {
        if (!Action.openapiFields.contains(entry.getKey())) {
          throw new IllegalArgumentException(String.format("The field `%s` in the JSON string is not defined in the `Action` properties. JSON: %s", entry.getKey(), jsonElement.toString()));
        }
      }
      
      // ...
}

The code I want would exclude that block or assign entries to Collections.emptySet()

Start with the Java generator's okhttp-gson/pojo.mustache template and inspect the validateJsonElement logic shown in the issue. The change is complete when generated model classes tolerate API properties unknown at generation time without raising the additional-field exception; no test file is named in the issue.