add Content Security Policy (#1252)

* add Content Security Policy

* remove reflect-metadata on production builds to get rid of unsafe-eval

* fix baseCSP usage

* add SRI to CSP

* add blob: to media-src

* remove SRI

* CSP set to reportOnly

* adding data: to connect-src CSP

* remove block-all-mixed-content

* add report-uri support

server.ts

@@ -53,6 +53,9 @@ if (errorMessage !== null) {
 app.set('trust proxy', CONFIG.TRUST_PROXY)
 
 // Security middleware
+import { baseCSP } from './server/middlewares'
+
+app.use(baseCSP)
 app.use(helmet({
   frameguard: {
     action: 'deny' // we only allow it for /videos/embed, see server/controllers/client.ts