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/init/init_directory_structure.sh.yaml

@@ -0,0 +1,64 @@
+suite: Init template
+release:
+  name: gitea-unittests
+  namespace: testing
+templates:
+  - templates/gitea/init.yaml
+tests:
+  - it: runs gpg in batch mode
+    set:
+      signing.enabled: true
+    asserts:
+      - equal:
+          path: stringData.[configure_gpg_environment.sh]
+          value: |-
+            #!/usr/bin/env bash
+            set -eu
+
+            gpg --batch --import /raw/private.asc
+  - it: skips gpg script block for disabled signing
+    asserts:
+      - equal:
+          path: stringData.[init_directory_structure.sh]
+          value: |-
+            #!/usr/bin/env bash
+
+            set -euo pipefail
+
+            set -x
+            chown 1000:1000 /data
+            mkdir -p /data/git/.ssh
+            chmod -R 700 /data/git/.ssh
+            [ ! -d /data/gitea/conf ] && mkdir -p /data/gitea/conf
+
+            # prepare temp directory structure
+            mkdir -p "${GITEA_TEMP}"
+            chown 1000:1000 "${GITEA_TEMP}"
+            chmod ug+rwx "${GITEA_TEMP}"
+  - it: adds gpg script block for enabled signing
+    set:
+      signing.enabled: true
+    asserts:
+      - equal:
+          path: stringData.[init_directory_structure.sh]
+          value: |-
+            #!/usr/bin/env bash
+
+            set -euo pipefail
+
+            set -x
+            chown 1000:1000 /data
+            mkdir -p /data/git/.ssh
+            chmod -R 700 /data/git/.ssh
+            [ ! -d /data/gitea/conf ] && mkdir -p /data/gitea/conf
+
+            # prepare temp directory structure
+            mkdir -p "${GITEA_TEMP}"
+            chown 1000:1000 "${GITEA_TEMP}"
+            chmod ug+rwx "${GITEA_TEMP}"
+
+            if [ ! -d "${GNUPGHOME}" ]; then
+              mkdir -p "${GNUPGHOME}"
+              chmod 700 "${GNUPGHOME}"
+              chown 1000:1000 "${GNUPGHOME}"
+            fi