Refactor db errors

internal/db/db_test.go

@@ -43,10 +43,10 @@ func testConnect(t *testing.T, ctx context.Context) {
 		t.Fatalf("Connect: %v", err)
 	}
 	if db.Writer == nil {
-		t.Fatal("Writer is nil")
+		t.Fatal("missing writer")
 	}
 	if db.Reader == nil {
-		t.Fatal("Reader is nil")
+		t.Fatal("missing reader")
 	}
 
 	// Test close.

internal/db/schema.go

@@ -28,7 +28,7 @@ var migrations embed.FS
 // the application code expects a schema that matches the latest migration.
 func (s *SQLite) ApplySchema(ctx context.Context, log *slog.Logger) error {
 	if log == nil {
-		return fmt.Errorf("logger is nil")
+		return fmt.Errorf("missing logger")
 	}
 
 	var currentVersion int