first pass server sent event based open AI chat API

chat.pm

my $ua = Mojo::UserAgent->new(max_response_size => 0);
	my $tx = $ua->build_tx(
		POST => 'https://api.openai.com/v1/chat/completions',
		+{
			Authorization => "Bearer $ENV{OPENAI_API_KEY}",
		},
		json => {
			model => "gpt-3.5-turbo",
			stream => \1,
   		messages => [
				{
					role => "user",
					content => $prompt,
				},
			],
		}
	);

	my $prior = '';
	$tx->res->content->unsubscribe('read')->on(read => sub ($content, $bytes) {
		if($prior) {
			$bytes = $prior.$bytes;
			$prior = '';
		}
		unless($bytes =~m/\n\n\z/) {
			$prior = $bytes;
			return 1;
		}
		my @messages = split 'data:', $bytes;
		while(@messages) {
			my $message = shift(@messages);
			next if $message eq '';
			next if $message =~m/\[DONE\]\n\n\z/;

			my $res = $json->decode($message);
			my $completion = $res->{choices}[0]{delta}{content};
			if($completion) {
				say $completion;
			} else {
				# is end of chat
			}
		}
	});
	$tx = $ua->start($tx);