feat(linkding): Add linkding stack

Bookmarking software similar to shaarli but a bit more featureful. And
not written in php, thankfully.

roles/linkding/tasks/main.yml

@@ -0,0 +1,23 @@
+---
+## install linkding container
+- name: Check upstream status
+  community.docker.docker_container_exec:
+    container: "{{ caddy_container_id }}"
+    command: >
+      curl localhost:2019/id/{{ stack_name }}_upstream/
+  register: result
+  changed_when: (result.stdout | from_json) != (lookup('template', 'upstream.json.j2') | from_yaml)
+  become: true
+  notify: "update linkding upstream"
+
+- name: Deploy linkding to swarm
+  community.general.docker_stack:
+    name: "{{ stack_name }}"
+    state: present
+    prune: yes
+    compose:
+      - "{{ stack_compose }}"
+  become: true
+  tags:
+    - docker-swarm
+  notify: "update linkding upstream"