Middleware: Add CSP support (#29740)

* Middleware: Add support for CSP

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

Co-authored by @iOrcohen

pkg/api/dtos/index.go

@@ -25,6 +25,8 @@ type IndexViewData struct {
 	AppleTouchIcon          template.URL
 	AppTitle                string
 	Sentry                  *setting.Sentry
+	// Nonce is a cryptographic identifier for use with Content Security Policy.
+	Nonce string
 }
 
 const (