Cache successful Blossom responses

Cache returned files from Blossom on the Nginx hosts, until either
deleted by the user or hitting the global cache size limit (1 GB)

site-cookbooks/kosmos_blossom/templates/default/nginx_conf_blossom.erb

@@ -19,7 +19,7 @@ server {
   ssl_certificate <%= @ssl_cert %>;
   ssl_certificate_key <%= @ssl_key %>;
 
-  location ~ ^/(?<sha256>[a-f0-9]{64})(\.[a-zA-Z0-9]+)?$ {
+  location ~ "^/(?<sha256>[a-f0-9]{64})(\.[a-zA-Z0-9]+)?$" {
     proxy_set_header Host $host;
     proxy_set_header X-Real-IP $remote_addr;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;