- duplicate X-Content-Type-Options
- X-Frame-Options header
- Referrer-Policy [Might consider adding variable]
- Secure flag with cookies
- matrix_grafana_content_security_policy variable for [Content Security Policy](https://grafana.com/docs/grafana/latest/administration/configuration/#content_security_policy)

It seems like it doesn't cause any issues for any of these services.

Also includes the dashboards for Synapse and for Node Exporter.

Again has only been tested on debian amd64 so far, but the grafana docker image is available for arm64 and arm32. Nice.