nostrdb: add supporting files for the bolt11 parser

A lot of this was pulled from core-lightning. Not sure what is actually
needed or not.

Signed-off-by: William Casarin <jb55@jb55.com>

nostrdb/bolt11/error.h

@@ -0,0 +1,33 @@
+
+#ifndef PROTOVERSE_ERROR_H
+#define PROTOVERSE_ERROR_H
+
+#include "cursor.h"
+
+struct error {
+	int pos;
+	const char *msg;
+};
+
+struct errors {
+	struct cursor cur;
+	int enabled;
+};
+
+#define note_error(errs, p, fmt, ...) note_error_(errs, p, "%s: " fmt, __FUNCTION__, ##__VA_ARGS__)
+
+static inline int cursor_push_error(struct cursor *cur, struct error *err)
+{
+	return cursor_push_int(cur, err->pos) &&
+	       cursor_push_c_str(cur, err->msg);
+}
+
+static inline int cursor_pull_error(struct cursor *cur, struct error *err)
+{
+	return cursor_pull_int(cur, &err->pos) &&
+	       cursor_pull_c_str(cur, &err->msg);
+}
+
+int note_error_(struct errors *errs, struct cursor *p, const char *fmt, ...);
+
+#endif /* PROTOVERSE_ERROR_H */