Add a var for ANSIBLE_MERGE_BEHAVIOUR=merge

[timetravlr]

We would like to have this be available as a variable to add to group_vars so it doesn't require doing this:

ANSIBLE_HASH_BEHAVIOUR=merge ansible-playbook -i inventories/site.yml confluent.platform.all --tags kafka_broker -l site-kafkatest-01 --skip-tags validate_hash_merge

cp-ansible/roles/common/tasks/main.yml requires this to be set in ansible.cfg or it fails.

- name: Confirm Hash Merging Enabled
  assert:
    that: lookup('config', 'DEFAULT_HASH_BEHAVIOUR') == 'merge'
    fail_msg: "Hash Merging must be enabled in ansible.cfg"
  tags:
    - validate
    - validate_hash_merge

We use a central repo and we cannot have hash behaviour = merge set globally in ansible.cfg, or it will cause problems. It is difficult to only set this for one of our collections or repos. I know other issues have been reported on this in the past.

[jceddy]

Also, I believe DEFAULT_HASH_BEHAVIOUR is deprecated as of 2.13...

[erikgb]

This issue is a duplicate of #474, and I think changing this would be a huge task in cp-ansible. That's why I marked the other issue as an "epic" back then.

But I think there is a new team at Confluent maintaining this project now. Maybe @mansisinha or @rrbadiani could take a look and/or forward the request to a product owner in Confluent?

[mansisinha]

@prabhamanepalli please have a look. We can analyse this more and include in our 2024 FF roadmap.