Add security headers to engineblock

[baszoetekouw]

This CSP header is reported to work:

Retrieved CSP value: ["default-src 'self'; font-src 'self'; style-src 'self' 'sha256-c823gKh+osiEtapTIYig0VtEe3NHj+8T2vWNPUjhcNQ=' 'sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU='; script-src 'unsafe-inline' 'self'; img-src 'self' https://*.openconext.org:* data:; frame-ancestors 'none'; form-action 'self' https:; base-uri 'none';"]

The style-src hash is necessary for the metadata page; the script-src: unsafe-inline for the json in the WAYF. Both should be fixed (by using an external stylesheet and by loading the json from an API-endpoint, respectively):

• WAYF pagina needs unsafe-inline CSP because of embedded json/js OpenConext-engineblock#1331
• Metadata page requires style-src hash in CSP OpenConext-engineblock#1332

frame-ancestors needs careful consideration.