fix(otel): accept full https:// URL in OTEL_EXPORTER_OTLP_ENDPOINT

WithEndpoint expects host[:port] with no scheme. When Doppler has
https://otel.libnovel.cc the backend was crashing with 'invalid port'.
Now strip the scheme and enable TLS when prefix is https://.

backend/internal/otelsetup/otelsetup.go

@@ -2,7 +2,10 @@
 //
 // It reads two environment variables:
 //
-//	OTEL_EXPORTER_OTLP_ENDPOINT  — OTLP/HTTP endpoint, e.g. http://otel-collector:4318
+//	OTEL_EXPORTER_OTLP_ENDPOINT  — OTLP/HTTP endpoint; accepts either a full
+//	                               URL ("https://otel.example.com") or a bare
+//	                               host[:port] ("otel-collector:4318").
+//	                               TLS is used when the value starts with "https://".
 //	OTEL_SERVICE_NAME            — service name reported in traces (default: "backend")
 //
 // When OTEL_EXPORTER_OTLP_ENDPOINT is empty the function is a no-op: it
@@ -21,6 +24,7 @@ import (
 	"fmt"
 	"log/slog"
 	"os"
+	"strings"
 	"time"
 
 	"go.opentelemetry.io/contrib/bridges/otelslog"
@@ -41,11 +45,17 @@ import (
 //   - logger:   an slog.Logger bridged to OTel logs (falls back to default when disabled).
 //   - err:      non-nil only on SDK initialisation failure.
 func Init(ctx context.Context, version string) (shutdown func(), logger *slog.Logger, err error) {
-	endpoint := os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT")
-	if endpoint == "" {
+	rawEndpoint := os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT")
+	if rawEndpoint == "" {
 		return nil, slog.Default(), nil // OTel disabled — not an error
 	}
 
+	// WithEndpoint expects a host[:port] value — no scheme.
+	// Support both "https://otel.example.com" and "otel-collector:4318".
+	useTLS := strings.HasPrefix(rawEndpoint, "https://")
+	endpoint := strings.TrimPrefix(rawEndpoint, "https://")
+	endpoint = strings.TrimPrefix(endpoint, "http://")
+
 	serviceName := os.Getenv("OTEL_SERVICE_NAME")
 	if serviceName == "" {
 		serviceName = "backend"
@@ -63,10 +73,11 @@ func Init(ctx context.Context, version string) (shutdown func(), logger *slog.Lo
 	}
 
 	// ── Trace provider ────────────────────────────────────────────────────────
-	traceExp, err := otlptracehttp.New(ctx,
-		otlptracehttp.WithEndpoint(endpoint),
-		otlptracehttp.WithInsecure(), // collector is on the internal Docker network
-	)
+	traceOpts := []otlptracehttp.Option{otlptracehttp.WithEndpoint(endpoint)}
+	if !useTLS {
+		traceOpts = append(traceOpts, otlptracehttp.WithInsecure())
+	}
+	traceExp, err := otlptracehttp.New(ctx, traceOpts...)
 	if err != nil {
 		return nil, slog.Default(), fmt.Errorf("otelsetup: create OTLP trace exporter: %w", err)
 	}
@@ -79,10 +90,11 @@ func Init(ctx context.Context, version string) (shutdown func(), logger *slog.Lo
 	otel.SetTracerProvider(tp)
 
 	// ── Log provider ──────────────────────────────────────────────────────────
-	logExp, err := otlploghttp.New(ctx,
-		otlploghttp.WithEndpoint(endpoint),
-		otlploghttp.WithInsecure(),
-	)
+	logOpts := []otlploghttp.Option{otlploghttp.WithEndpoint(endpoint)}
+	if !useTLS {
+		logOpts = append(logOpts, otlploghttp.WithInsecure())
+	}
+	logExp, err := otlploghttp.New(ctx, logOpts...)
 	if err != nil {
 		return nil, slog.Default(), fmt.Errorf("otelsetup: create OTLP log exporter: %w", err)
 	}