Add migration task for Debiant apt repositories for Docker referencing /etc/apt/keyrings/docker.asc key

Related to:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3337
- https://github.com/geerlingguy/ansible-role-docker/pull/436

roles/custom/matrix_playbook_migration/defaults/main.yml

@@ -43,6 +43,16 @@ matrix_playbook_migration_matrix_jitsi_migration_validation_enabled: true
 matrix_playbook_migration_debian_signedby_migration_enabled: true
 matrix_playbook_migration_debian_signedby_migration_repository_path: "/etc/apt/sources.list.d/download_docker_com_linux_{{ ansible_distribution | lower }}.list"
 
+# Controls if the old apt repository for Docker (`signed-by=/etc/apt/trusted.gpg.d/docker.asc`) will be removed,
+# so that the Docker role (7.2.0+) can install a new non-conflicting one (`signed-by=/etc/apt/keyrings/docker.asc`).
+#
+# Without this migration, the role would choke at the "galaxy/docker : Add Docker repository." task when trying to add the repository again:
+# > An exception occurred during task execution. To see the full traceback, use -vvv. The error was: apt_pkg.Error: E:Conflicting values set for option Signed-By regarding source https://download.docker.com/linux/ubuntu/ focal: /etc/apt/trusted.gpg.d/docker.asc != /etc/apt/keyrings/docker.asc, E:The list of sources could not be read.
+#
+# Related to: https://github.com/geerlingguy/ansible-role-docker/pull/436
+matrix_playbook_migration_docker_trusted_gpg_d_migration_enabled: true
+matrix_playbook_migration_docker_trusted_gpg_d_migration_repository_path: "/etc/apt/sources.list.d/docker.list"
+
 # Controls if variable transition checks (related to the matrix-nginx-proxy elimination) will run.
 # If you'd like to keep some `matrix_nginx_proxy` and other variables around and not be warned about them, disable this.
 # Note: this is not just about `matrix_nginx_proxy_*` variables, but about various other variables that were removed