HACK: Track goroutine IDs to determine when we write by the wrong thread

To use: set `DENDRITE_TRACE_SQL=1` then grep for `unsafe`

internal/sqlutil/writer.go

@@ -43,4 +43,6 @@ type Writer interface {
 	// Queue up one or more database write operations within the
 	// provided function to be executed when it is safe to do so.
 	Do(db *sql.DB, txn *sql.Tx, f func(txn *sql.Tx) error) error
+
+	Safe() string
 }