Vendor middleware_automation.keycloak collection

Needed for keycloak_authentication_v2, to manage Keycloak
authentication flows (e.g. the CCCHH browser flow) as YAML.
Chosen over community.general's own copy of the module (deprecated in
favor of this collection, and limited to 4 sub-flow levels there vs.
10 here).

ansible_collections/middleware_automation/keycloak/CONTRIBUTING.md

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+## Developing
+
+### Build and install locally
+
+Clone the repository, checkout the tag you want to build, or pick the main branch for the development version; then:
+
+    ansible-galaxy collection build .
+    ansible-galaxy collection install middleware_automation-keycloak-*.tar.gz
+
+
+### Development environment
+
+Make sure your development machine has avilable:
+
+* python 3.11+
+* virtualenv
+* docker (or podman)
+
+In order to run setup the development environment and run the molecule tests locally, after cloning the repository:
+
+```
+# create new virtualenv using python 3
+virtualenv $PATH_TO_DEV_VIRTUALENV
+# activate the virtual env
+source $PATH_TO_DEV_VIRTUALENV/bin/activate
+# install ansible and tools onto the virtualenv
+pip install yamllint 'molecule>=6.0' 'molecule-plugins[docker]' 'ansible-core>=2.16' ansible-lint
+# install collection dependencies
+ansible-galaxy collection install -r requirements.yml
+# install python dependencies
+pip install -r requirements.txt molecule/requirements.txt
+# execute the tests (replace --all with -s subdirectory to run a single test)
+molecule test --all
+```
+
+## Contributor's Guidelines
+
+- All YAML files named with `.yml` extension
+- Use spaces around jinja variables. `{{ var }}` over `{{var}}`
+- Variables that are internal to the role should be lowercase and start with the role name
+- Keep roles self contained - Roles should avoid including tasks from other roles when possible
+- Plays should do nothing more than include a list of roles, except where `pre_tasks` and `post_tasks` are required, when possible
+- Separators - Use valid names, ie. underscores (e.g. `my_role` `my_playbook`) not dashes (`my-role`)
+- Paths - When defining paths, do not include trailing slashes (e.g. `my_path: /foo` not `my_path: /foo/`); when concatenating paths, follow the same convention (e.g. `{{ my_path }}/bar` not `{{ my_path }}bar`)
+- Indentation - Use 2 spaces for each indent
+- `vars/` vs `defaults/` - internal or interpolated variables that don't need to change or be overridden by user go in `vars/`, those that a user would likely override, go under `defaults/` directory
+- All role arguments have a specification in `meta/argument_specs.yml`
+- All playbooks/roles should be focused on compatibility with Ansible Automation Platform