This commit changes how we eager-load projects, routes, and namespaces
required by the deploy keys endpoint, getting a 10x improvement in my
local testing.
The endpoint still doesn't scale in-general, but going from ~13 seconds
to dump a 63K result to generating the same thing in ~1.6 seconds seems
like a good improvement to me.
Added specs for the deploy_keys_presenter and added a new method in the presenter
called #key_available?
Fixed some minor UX inconsistencies and added a concern to handle
redirection
