BAU: Ban search robots from indexing pages
BAU: Ban search robots from indexing pages

Setting the meta tag is not enough on error pages as Googlebot doesn't read it.
This uses the existing flag to append the header.

I also considered using the nginx rules, but it would be a bit more complex with the
conditions as we actually control the pages from frontend.

alphagov/verify-frontend,alphagov/verify-frontend,alphagov/verify-frontend,alphagov/verify-frontend