Add Helm chart (#14090)

* add Helm chart

known issues/future work:

- SSO is unsupported

- S3/Minio/GCS is unsupported

- Swift is unsupported

- WEB_DOMAIN is unsupported

- Tor is unsupported

* helm: clarify how LOCAL_DOMAIN is set

* helm: add chart description

* helm: make DB_POOL and Sidekiq concurrency configurable

* helm: only enforce pod affinity when using ReadWriteOnce

* helm: clarify compatibility

* helm: clean up application variables

* helm: add job to create initial admin

chart/Chart.yaml

@@ -0,0 +1,35 @@
+apiVersion: v2
+name: mastodon
+description: Mastodon is a free, open-source social network server based on ActivityPub.
+
+# A chart can be either an 'application' or a 'library' chart.
+#
+# Application charts are a collection of templates that can be packaged into versioned archives
+# to be deployed.
+#
+# Library charts provide useful utilities or functions for the chart developer. They're included as
+# a dependency of application charts to inject those utilities and functions into the rendering
+# pipeline. Library charts do not define any templates and therefore cannot be deployed.
+type: application
+
+# This is the chart version. This version number should be incremented each time you make changes
+# to the chart and its templates, including the app version.
+# Versions are expected to follow Semantic Versioning (https://semver.org/)
+version: 0.1.0
+
+# This is the version number of the application being deployed. This version number should be
+# incremented each time you make changes to the application. Versions are not expected to
+# follow Semantic Versioning. They should reflect the version the application is using.
+appVersion: 3.1.4
+
+dependencies:
+  - name: elasticsearch
+    version: "12.x.x"
+    repository: https://charts.bitnami.com/bitnami
+    condition: elasticsearch.enabled
+  - name: postgresql
+    version: "8.x.x"
+    repository: https://charts.bitnami.com/bitnami
+  - name: redis
+    version: "10.x.x"
+    repository: https://charts.bitnami.com/bitnami