Introduce POST size limit for ORA submissions

The ORA machinery gets gummed up when it gets very large submissions and
throws a lot of 500s.

Co-Authored-By: Jason Bau <jbau@stanford.edu>

playbooks/roles/nginx/templates/ora.j2

@@ -34,6 +34,7 @@ server {
   }
 
   location @proxy_to_app {
+    client_max_body_size 75K;
     proxy_set_header X-Forwarded-Proto $http_x_forwarded_proto;
     proxy_set_header X-Forwarded-Port $http_x_forwarded_port;
     proxy_set_header X-Forwarded-For $http_x_forwarded_for;