Re-add GPG configuration feature (#374)

This reverts d5ce1a47ea and therefore adds the GPG feature back into main.
As it is a breaking change, this PR now also contains the required upgrade notes.

Closes #107 again.

Co-authored-by: justusbunsi <sk.bunsenbrenner@gmail.com>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/374
Reviewed-by: pat-s <pat-s@noreply.gitea.io>
Reviewed-by: John Olheiser <john+gitea@jolheiser.com>

unittests/statefulset/basic.yaml

@@ -0,0 +1,17 @@
+suite: Statefulset template (basic)
+release:
+  name: gitea-unittests
+  namespace: testing
+templates:
+  - templates/gitea/statefulset.yaml
+  - templates/gitea/config.yaml
+tests:
+  - it: renders a statefulset
+    template: templates/gitea/statefulset.yaml
+    asserts:
+      - hasDocuments:
+          count: 1
+      - containsDocument:
+          kind: StatefulSet  
+          apiVersion: apps/v1
+          name: gitea-unittests