Also make sure cowboy always read the whole data in the handler (or returns an error if it's too large)

[E 2023-04-20 11:05:43.166 <0.4114.2>] An unexpected exception occurred in rest_handler:process_request/2 line 301
> Stacktrace:
proc_lib:init_p_do_apply/3 line 240
cowboy_stream_h:request_process/3 line 295
cowboy_stream_h:execute/3 line 306
cowboy_rest:upgrade/4 line 284
cowboy_rest:process_content_type/3 line 1096
cowboy_rest:call/3 line 1583
rest_handler:process_request/2 line 283
rest_handler:get_data/1 line 432
> Details: Unexpected error in rest_handler:process_request - error:{badmatch,
{more,
...