Add ansible collection support

[tod-uma]

Why

This makes it possible to consume splunk-ansible as an Ansible collection — installed via ansible-galaxy collection install from a git-sourced requirements.yml — instead of vendoring or symlinking the repo into a project's roles path. That's useful for anyone integrating splunk-ansible's roles into their own playbooks (for example, installing the universal forwarder as one step of a broader Ansible-managed bootstrap process) without maintaining a private fork just to get collection semantics.

Ansible collections need two things this repo doesn't have: a galaxy.yml manifest, and modules living under plugins/modules/ rather than library/ (library/ is the pre-collection, role-local module path; a collection's own modules resolve from plugins/modules/ — see Developing collections).

What

• galaxy.yml (new) — collection manifest. description, license (matches the repo's actual Apache-2.0 license), tags, and documentation/homepage/issues links to the existing docs site, repo, and issue tracker. version starts at 1.0.0: a collection's version should track its own release history, not whatever Splunk build happens to be current, so it isn't tied to a product version number.
• library/ → plugins/modules/ — moves splunk_api.py and es_ta_for_indexers.py to the path a collection resolves its modules from. Done as renames (git mv), so history is preserved on both files.

Verified

ansible-galaxy collection build succeeds and produces a valid splunk-splunk_ansible-1.0.0.tar.gz.

Once installed as a collection:

# collections/requirements.yml
collections:
  - source: https://github.com/splunk/splunk-ansible.git
    version: "10.4.3"   # pin a release tag, not a moving branch
    type: git

# playbook.yml
- hosts: splunk_universal_forwarder
  become: true
  collections:
    - splunk.splunk_ansible
  vars:
    splunk: "{{ splunk_universal_forwarder }}"
  tasks:
    - name: install the forwarder
      ansible.builtin.include_role:
        name: splunk_universal_forwarder

Status

Opened in 2024 and stale since; rebased now onto current develop with no conflicts — this range hasn't touched library/ or galaxy.yml, so both structural changes still apply cleanly. We've been running this on a fork since, alongside several other fixes that have since merged cleanly here (#879, #883, #893, #894), so happy to adjust anything in galaxy.yml — tags especially — to whatever fits the project's own preference.

[tod-uma]

Rebased onto current develop (no conflicts — this range hasn't touched library/ or galaxy.yml), filled in galaxy.yml's description/license/tags/links, and reset the version to 1.0.0 so it tracks the collection's own history rather than a Splunk build number. Description above has the details.

We've been running this on a fork for a while now, alongside several other small fixes that have since merged cleanly here — #879, #883, #893, #894 — so figured it was worth bringing this one back into view too. Happy to adjust anything, galaxy.yml's tags especially, to match project preference.