Initial work on using externally defined roles

roles/custom/matrix_playbook_migration/tasks/main.yml

@@ -0,0 +1,5 @@
+---
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/validate_config.yml"
+  tags:
+    - setup-all

roles/custom/matrix_playbook_migration/tasks/validate_config.yml

@@ -0,0 +1,12 @@
+---
+
+- name: (Deprecation) Catch and report renamed Matrix playbook settings
+  ansible.builtin.fail:
+    msg: >-
+      Your configuration contains a variable, which now has a different name.
+      Please change your configuration to rename the variable (`{{ item.old }}` -> `{{ item.new }}`).
+  when: "item.old in vars"
+  with_items:
+    - {'old': 'matrix_vars_yml_snapshotting_enabled', 'new': 'devture_playbook_state_preserver_vars_preservation_enabled'}
+    - {'old': 'matrix_vars_yml_snapshotting_src', 'new': 'devture_playbook_state_preserver_vars_preservation_src'}
+    - {'old': 'matrix_playbook_commit_hash_preservation_enabled', 'new': 'devture_playbook_state_preserver_commit_hash_preservation_enabled'}