install syncthing via PPA

roles/syncthing/tasks/main.yml

@@ -1,3 +1,19 @@
+- name: Download PPA signing key
+  become: true
+  apt_key:
+    keyserver: keyserver.ubuntu.com
+    id: "37C84554E7E0A261E4F76E1ED26E6ED000654A3E"
+    keyring: /etc/apt/keyrings/syncthing.gpg
+- name: Install APT repository
+  become: true
+  apt_repository:
+    repo: "deb [signed-by=/etc/apt/keyrings/syncthing.gpg] https://apt.syncthing.net/ syncthing stable"
+  register: apt_repository
+- name: Update APT cache
+  become: true
+  apt:
+    update_cache: true
+  when: apt_repository.changed
 - name: Install Syncthing
   become: true
   apt: