Implement equals and hashcode method into generated classes

[pawel-big-lebowski]

Implement equals and hashcode method into generated classes.

Example methods generated:

    @Override
    public boolean equals(Object o) {
      if (this == o) return true;
      if (o == null || getClass() != o.getClass()) return false;
      Run that = (Run) o;
      if (!Objects.equals(runId, that.runId)) return false;
      if (!Objects.equals(facets, that.facets)) return false;
      return true;
    }

    @Override
    public int hashCode() {
      return Objects.hash(runId, facets);
    }

The change is required for PR 3996 to detect that two daasets have the same facets.

[julienledem]

LGTM!

[julienledem]

nit: I would also add a negative case. something like:

Run differentRun = ol.newRunBuilder().runId(UUID.randomUUID()).facets(runFacets).build();
assertThat(run.hashCode()).isNotEqualTo(differentRun.hashCode())
assertThat(run).isNotEqualTo(differentRun);