Add basic caddy swarm role

Added caddy as swarm container. Uses templated Caddyfile which can be
set up for testing purposes for now.
Depends on docker and docker-swarm, and will keep its stuff where
docker-swarm sets itself up.

roles/caddy/tasks/main.yml

@@ -0,0 +1,27 @@
+---
+# install caddy as a docker stack
+
+- name: Ensure Caddyfile directory exists
+  ansible.builtin.file:
+    path: "{{ caddy_caddyfile_dir }}"
+    state: directory
+    mode: '0755'
+  become: true
+
+- name: Ensure Caddyfile exists
+  ansible.builtin.template:
+    src: Caddyfile.j2
+    dest: "{{ caddy_caddyfile_dir }}/Caddyfile"
+    validate: "docker run --rm -v %s:/Caddyfile caddy caddy validate --config /Caddyfile"
+  become: true
+
+- name: Deploy caddy to swarm
+  community.general.docker_stack:
+    name: "{{ item.name }}"
+    state: present
+    prune: yes
+    compose:
+      - "{{ item.compose }}"
+  with_items: "{{ caddy_stack }}"
+  when: caddy_stack is defined
+  become: yes