r/dch-yum: Trust GPG key

We need to explicitly add the GPG signing key for the _dch_ repository
to the system trust store, otherwise, _dnf-automatic_ will fail, as it
cannot implicitly add new keys during an update.

roles/dch-yum/tasks/main.yml

@@ -7,3 +7,10 @@
     mode: u=rw,go=r
   tags:
   - repo
+
+- name: ensure dch rpm gpg key is trusted
+  rpm_key:
+    key: https://files.pyrocufflink.blue/yum/dch/gnupg.pub
+    state: present
+  tags:
+  - rpm-key