test: cover root configuration with Molecule

Verify SSH key rotation, file permissions, optional file removal and password management on Arch Linux, Debian and Fedora. Keep container dependencies scoped to the test scenario.

Co-authored-by: Copilot <copilot@github.com>

molecule/default/create.yml

@@ -0,0 +1,41 @@
+---
+- name: Create
+  hosts: localhost
+  gather_facts: false
+  tasks:
+  - name: Start a container per platform
+    community.docker.docker_container:
+      name: "{{ item.name }}"
+      image: "{{ item.image }}"
+      command: sleep infinity
+      state: started
+    loop: "{{ molecule_yml.platforms }}"
+    loop_control:
+      label: "{{ item.name }}"
+
+  - name: Write the instance config
+    ansible.builtin.copy:
+      content: |
+        {% for platform in molecule_yml.platforms %}
+        - instance: {{ platform.name }}
+          connection: community.docker.docker
+        {% endfor %}
+      dest: "{{ molecule_instance_config }}"
+      mode: "0600"
+
+  - name: Generate temporary SSH key pairs
+    ansible.builtin.command:
+      argv:
+      - ssh-keygen
+      - -t
+      - ed25519
+      - -N
+      - ""
+      - -C
+      - molecule-root
+      - -f
+      - "{{ molecule_ephemeral_directory }}/{{ item }}"
+      creates: "{{ molecule_ephemeral_directory }}/{{ item }}"
+    loop:
+    - original.ed25519
+    - replacement.ed25519