docker_compose(role): add support for deploying optional .env file

This is needed for situations, where one wants to use a vendor-provided
compose file and configure it using environment variables.
Like for example:
https://github.com/zammad/zammad-docker-compose

roles/docker_compose/README.md

@@ -1,8 +1,8 @@
 # Role `docker_compose`
 
 A role for deploying a Docker-Compose-based application.
-It deploys the given Compose file as well as configuration files to the specified hosts and makes sure all services are up-to-date and running.
-The Compose file gets deployed to `/ansible_docker_compose/compose.yaml` and the configuration files get deployed into the `/ansible_docker_compose/configs/` directory.
+It deploys the given Compose file, an optional `.env` file, as well as configuration files to the specified hosts and makes sure all services are up-to-date and running.
+The Compose file gets deployed to `/ansible_docker_compose/compose.yaml`, the `.env` file to `/ansible_docker_compose/.env` and the configuration files get deployed into the `/ansible_docker_compose/configs/` directory.
 A use case for the deployment of the additional configuration files is Composes top-level element `configs` in conjunction with the `configs` option for services.
 
 ## Supported Distributions

roles/docker_compose/meta/argument_specs.yaml

@@ -7,6 +7,12 @@ argument_specs:
           `/ansible_docker_compose/compose.yaml`.
         type: str
         required: true
+      docker_compose__env_file_content:
+        description: >-
+          The content of the .env file at
+          `/ansible_docker_compose/.env`.
+        type: str
+        required: false
       docker_compose__configuration_files:
         description: >-
           A list of configuration files to be deployed in the

roles/docker_compose/tasks/main.yaml

@@ -17,6 +17,17 @@
   become: true
   notify: docker compose down
 
+- name: deploy the .env file
+  ansible.builtin.copy:
+    content: "{{ docker_compose__env_file_content }}"
+    dest: /ansible_docker_compose/.env
+    mode: "0644"
+    owner: root
+    group: root
+  become: true
+  when: docker_compose__env_file_content is defined
+  notify: docker compose down
+
 - name: make sure the `/ansible_docker_compose/configs` directory exists
   ansible.builtin.file:
     path: /ansible_docker_compose/configs