-// POST /foo.txt
-// Content-Type: application/x-www-form-urlencoded
-// [...]
-// api_token=o07j4px7RlJK4CuMYp7C0LDT4CzR1J1qBE5Avo7eCcUjOTikxK
-//
-// If a token is provided in a query string or in a POST request, the
-// response is an HTTP 303 redirect to an equivalent GET request, with
-// the token stripped from the query string and added to a cookie
-// instead.
-//
-// Compatibility
-//
-// Client-provided authorization tokens are ignored if the client does
-// not provide a Host header.
-//
-// In order to use the query string or a POST form authorization
-// mechanisms, the client must follow 303 redirects; the client must
-// accept cookies with a 303 response and send those cookies when
-// performing the redirect; and either the client or an intervening
-// proxy must resolve a relative URL ("//host/path") if given in a
-// response Location header.
-//
-// Intranet mode
-//
-// Normally, Keep-web accepts requests for multiple collections using
-// the same host name, provided the client's credentials are not being
-// used. This provides insufficient XSS protection in an installation
-// where the "anonymously accessible" data is not truly public, but
-// merely protected by network topology.
-//
-// In such cases -- for example, a site which is not reachable from
-// the internet, where some data is world-readable from Arvados's
-// perspective but is intended to be available only to users within
-// the local network -- the upstream proxy should configured to return
-// 401 for all paths beginning with "/c=".
-//
-// Same-origin mode
-//
-// Without the same-origin protection outlined above, a web page
-// stored in collection X could execute JavaScript code that uses the
-// current viewer's credentials to download additional data from
-// collection Y -- data which is accessible to the current viewer, but
-// not to the author of collection X -- from the same origin
-// (``https://dl.example.com/'') and upload it to some other site
-// chosen by the author of collection X.
-//
-package main
-
-// TODO(TC): Implement
-//
-// Trusted content
-//
-// Normally, Keep-web is installed using a wildcard DNS entry and a
-// wildcard HTTPS certificate, serving data from collection X at
-// ``https://X--dl.example.com/path/file.ext''.
-//
-// It will also serve publicly accessible data at
-// ``https://dl.example.com/collections/X/path/file.txt'', but it does not
-// accept any kind of credentials at paths like these.
-//
-// In "trust all content" mode, Keep-web will accept credentials (API