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>

templates/gitea/init.yaml

@@ -6,6 +6,11 @@ metadata:
     {{- include "gitea.labels" . | nindent 4 }}
 type: Opaque
 stringData:
+  configure_gpg_environment.sh: |-
+    #!/usr/bin/env bash
+    set -eu
+
+    gpg --batch --import /raw/private.asc
   init_directory_structure.sh: |-
     #!/usr/bin/env bash
 
@@ -35,6 +40,14 @@ stringData:
     {{- end }}
     chmod ug+rwx "${GITEA_TEMP}"
 
+    {{ if .Values.signing.enabled -}}
+    if [ ! -d "${GNUPGHOME}" ]; then
+      mkdir -p "${GNUPGHOME}"
+      chmod 700 "${GNUPGHOME}"
+      chown 1000:1000 "${GNUPGHOME}"
+    fi
+    {{- end }}
+
   configure_gitea.sh: |-
     #!/usr/bin/env bash