Restructured libraries

filter_plugins/README.md

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+# Custom Filter Plugins for CyMaIS
+
+This directory contains custom **Ansible filter plugins** used within the CyMaIS project.
+
+## When to Use a Filter Plugin
+
+- **Transform values:** Use filters to transform, extract, reformat, or compute values from existing variables or facts.
+- **Inline data manipulation:** Filters are designed for inline use in Jinja2 expressions (in templates, tasks, vars, etc.).
+- **No external lookups:** Filters only operate on data you explicitly pass to them and cannot access external files, the Ansible inventory, or runtime context.
+
+### Examples
+
+```jinja2
+{{ role_name | get_entity_name }}
+{{ my_list | unique }}
+{{ user_email | regex_replace('^(.+)@.*$', '\\1') }}
+````
+
+## When *not* to Use a Filter Plugin
+
+* If you need to **load data from an external source** (e.g., file, environment, API), use a lookup plugin instead.
+* If your logic requires **access to inventory, facts, or host-level information** that is not passed as a parameter.
+
+## Further Reading
+
+* [Ansible Filter Plugins Documentation](https://docs.ansible.com/ansible/latest/plugins/filter.html)
+* [Developing Ansible Filter Plugins](https://docs.ansible.com/ansible/latest/dev_guide/developing_plugins.html#developing-filter-plugins)