Prepare GovOPlaN self-hosted release workflow

.env.example

@@ -0,0 +1,32 @@
+# GovOPlaN self-hosted install configuration.
+# Copy to a deployment-local .env or secret store. Do not commit populated secrets.
+
+APP_ENV=production
+GOVOPLAN_INSTALL_PROFILE=self-hosted
+MASTER_KEY_B64=<generate-with-govoplan-config-env-template-generate-secrets>
+
+DATABASE_URL=postgresql+psycopg://govoplan:change-me@127.0.0.1:5432/govoplan
+GOVOPLAN_DATABASE_URL_PGTOOLS=postgresql://govoplan:change-me@127.0.0.1:5432/govoplan
+
+ENABLED_MODULES=tenancy,organizations,identity,access,admin,dashboard,policy,audit,files,mail,campaigns,calendar,docs,ops
+
+CELERY_ENABLED=true
+REDIS_URL=redis://127.0.0.1:6379/0
+CELERY_QUEUES=send_email,append_sent,default
+
+CORS_ORIGINS=https://govoplan.example.org
+AUTH_COOKIE_SECURE=true
+AUTH_COOKIE_SAMESITE=lax
+AUTH_COOKIE_DOMAIN=
+
+FILE_STORAGE_BACKEND=local
+FILE_STORAGE_LOCAL_ROOT=/var/lib/govoplan/files
+FILE_STORAGE_LOCAL_FALLBACK_ROOTS=
+
+DEV_AUTO_MIGRATE_ENABLED=false
+DEV_BOOTSTRAP_ENABLED=false
+DEV_MAILBOX_API_ENABLED=false
+
+GOVOPLAN_MODULE_PACKAGE_CATALOG_URL=https://govoplan.add-ideas.de/catalogs/v1/channels/stable.json
+GOVOPLAN_MODULE_PACKAGE_CATALOG_TRUSTED_KEYS_FILE=/etc/govoplan/catalog-keyring.json
+GOVOPLAN_MODULE_PACKAGE_CATALOG_APPROVED_CHANNEL=stable