Reorganize API types so hlint can parse them
Reorganize API types so hlint can parse them

Split the caching-related 'Header's and type-list into type aliases,
then use them. For some reason hlint has no trouble parsing them like
this.

Also: make all of the places we do caching headers do the *same*
caching headers.

jasonzoladz/oauth2-server,anchor/oauth2-server