Dream.flash_message should provide debug mode

[thangngoc89]

From my experience adding flash message, it could be extremely frustrating to debug why flash messages aren't rendered at all.

I wrote this little middleware to help with debugging but this should probably be added to Dream.flash_message directly

type flash = (string * string) list [@@deriving show]

let debug_flash inner_handler request =
  let%lwt response = inner_handler request in
  let local = Dream.get_flash request in
  Dream.log "flash messages: %s" (show_flash local) ;
  Lwt.return response

[aantron]

I guess there should probably be a dream.flash log source. Dream also needs a neat way to set the log level per-source, and then flash messages need documentation about the existence of verbose logging on dream.flash at level debug. Would that do?

[aantron]

A good place for such documentation might be the not-yet-integrated flash message example, which also needs a README.

[aantron]

The flash message middleware should probably also warn if the whole encrypted cookie is more than 4096 bytes long.

[jsthomas]

I'm interested in working on this issue.