[JAVA] Bug found in RFC3339DateFormat about clone method

Created by: fcanovas1986

Description

We have been noticed by a bug in this class from spotbugs-maven-plugin. When generating the RFC3339DateFormat class:

[ERROR] Medium:xxxxxxxx.rest.client.invoker.RFC3339DateFormat.clone() does not call super.clone() [xxxxxxxxxx.rest.client.invoker.RFC3339DateFormat] At RFC3339DateFormat.java:[line 53] CN_IDIOM_NO_SUPER_CALL

If I check the class template RFC3339DateFormat.mustache I can see how it is true that the override method clone() does not call super.clone(). It only calls return this;, so it is not cloning the object.

@Override
  public Object clone() {
    return this;
  }

Find the reference to this bug here

openapi-generator version

5.3.0

Suggest a fix/enhancement

Calling super.clone method inside clone() method of RFC3339DateFormat would be enough. I would be happy to contribute if you want.