feat: add CSP and other security related headers in the oCIS proxy service (#8777)

* feat: add CSP and other security related headers in the oCIS proxy service

* fix: consolidate security related headers - drop middleware.Secure

* fix: use github.com/DeepDiver1975/secure

* fix: acceptance tests

* feat: support env var replacements in csp.yaml

vendor/github.com/unrolled/secure/doc.go

@@ -0,0 +1,26 @@
+/*
+Package secure is an HTTP middleware for Go that facilitates some quick security wins.
+
+	package main
+
+	import (
+	    "net/http"
+
+	    "github.com/unrolled/secure"
+	)
+
+	var myHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	    w.Write([]byte("hello world"))
+	})
+
+	func main() {
+	    secureMiddleware := secure.New(secure.Options{
+	        AllowedHosts: []string{"www.example.com", "sub.example.com"},
+	        SSLRedirect:  true,
+	    })
+
+	    app := secureMiddleware.Handler(myHandler)
+	    http.ListenAndServe("127.0.0.1:3000", app)
+	}
+*/
+package secure