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Currently only the lookup plugins from this collection support passing the connection credentials via environment variables, inventory and module plugins don't:

export ANSIBLE_LOOKUP_CHECKMK_SERVER_URL="https://myserver"
export ANSIBLE_LOOKUP_CHECKMK_SITE=mysite
export ANSIBLE_LOOKUP_CHECKMK_AUTOMATION_USER=automation
export ANSIBLE_LOOKUP_CHECKMK_AUTOMATION_SECRET=mysecret
export ANSIBLE_LOOKUP_CHECKMK_VALIDATE_CERTS=False

This was implemented in #546.

However, there is a problem with this implementation, when using AWX/Ansible Automation Platform: It is disallowed to create a custom Credential Type with "ANSIBLE_*" env-vars injector configurations:

Environment variable ANSIBLE_LOOKUP_CHECKMK_AUTOMATION_SECRET may affect Ansible configuration so its use is not allowed in credentials.

Which makes sense, as ANSIBLE_* env-vars are "traditionally" reserved for ansible-core configurations and not for third party collections. Judging from several other third party collections, the usual naming scheme seems to be just a prefix of the managed product/namespace, e.g. "CHECKMK_". For a transition period I would suggest adding env-vars with a compatible naming schema (e.g. CHECKMK_SERVER_URL, CHECKMK_SITE, CHECKMK_AUTOMATION_SECRET, etc) and keep the current names as fallbacks.

Additionally it would make sense to implement the support for the env-vars in inventory plugins and modules as well. Plugins all use the same way to parse enviroment variables for parameters (via DOCUMENTATION docstring, also able to externalize that via doc_fragments), modules use the argspec fallback option with env_fallback, as for example seen here: https://github.com/ansible-collections/community.vmware/blob/main/plugins/module_utils/_argument_spec.py

Collection Version
v5.8.0