Name the municipality when the CEP does not existv0.2.0

Answering only "não encontrei" wastes the trip. A CEP that fails is
almost never a random number: it is someone who knows the city and
guessed the rest, most often at the "-000" that 957 municipalities never
received. The API now names that municipality on the 404, so the reply
names it too.

It stays an answer to a failure. No 📮, no address block, and no CEP
suggested from inside the range — the range is sparse (Areal's 118 CEPs
span nearly five thousand numbers), so the reply gives the count and says
so instead of letting the two ends read as a list of valid CEPs.

cep.is/go v0.1.0 discards the 404 body, so internal/lookup reads it with
one extra GET, on that path alone and never inside a retry. Everything
that can go wrong there — a slow answer, broken JSON, a faixa naming no
municipality — falls back to the reply the bot has always given. The
wrapper goes away the day the library exposes the field.

1 files changed, 9 insertions, 2 deletions

diff --git a/internal/app/app.go b/internal/app/app.go
index 0b78baf..ccb8483 100644
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -15,6 +15,7 @@ import (
 
 	"cep.is/telegrambot/internal/bot"
 	"cep.is/telegrambot/internal/config"
+	"cep.is/telegrambot/internal/lookup"
 	"cep.is/telegrambot/internal/telegram"
 )
 
@@ -34,22 +35,28 @@ type App struct {
 // The whole-call timeout of the cep.is client is the shutdown grace on purpose:
 // handling one update is what a termination signal waits for, so a lookup must
 // not be allowed to outlast that budget.
+//
+// The client goes to the bot wrapped in [lookup.Client], which is what keeps the
+// municipality the API names on a 404. The wrapper has its own short timeout,
+// deliberately far below the grace: it is a footnote on an answer that is
+// already writable.
 func New(ctx context.Context, cfg config.Config, logger *slog.Logger) (*App, error) {
 	if logger == nil {
 		logger = slog.Default()
 	}
 
-	lookups, err := cepis.New(
+	cepisClient, err := cepis.New(
 		cepis.WithBaseURL(cfg.CepisBaseURL),
 		cepis.WithTimeout(cfg.RequestTimeout),
 		cepis.WithMaxAttempts(cfg.MaxAttempts),
 		cepis.WithBackoff(cfg.BackoffBase, cfg.BackoffMax),
 		cepis.WithTotalTimeout(cfg.ShutdownGrace),
-		cepis.WithUserAgent("cepis-telegram/0.1.0 (+https://cep.is)"),
+		cepis.WithUserAgent("cepis-telegram/0.2.0 (+https://cep.is)"),
 	)
 	if err != nil {
 		return nil, fmt.Errorf("app: cep.is client: %w", err)
 	}
+	lookups := lookup.New(cepisClient)
 
 	api, err := telegram.New(cfg.Token,
 		telegram.WithBaseURL(cfg.TelegramAPIBaseURL),