Said fields in statistics are of type
`disk_array<uint32_t, disk_string<uint16_t>>` and currently are handled
as array of regular strings. However these fields store exploded
clustering keys, so the elements store binary data and converting to
string can yield invalid UTF-8 characters that certain JSON parsers (jq,
or python's json) can choke on. Fix this by treating them as binary and
using `to_hex()` to convert them to string. This requires some massaging
of the json_dumper: passing field offset to all visit() methods and
using a caller-provided disk-string to sstring converter to convert disk
strings to sstring, so in the case of statistics, these fields can be
intercepted and properly handled.
While at it, the type of these fields is also fixed in the
documentation.
Before:
"min_column_names": [
"��Z���\u0011�\u0012ŷ4^��<",
"�2y\u0000�}\u007f"
],
"max_column_names": [
"��Z���\u0011�\u0012ŷ4^��<",
"}��B\u0019l%^"
],
After:
"min_column_names": [
"9dd55a92bc8811ef12c5b7345eadf73c",
"80327900e2827d7f"
],
"max_column_names": [
"9dd55a92bc8811ef12c5b7345eadf73c",
"7df79242196c255e"
],
Fixes: #22078Closesscylladb/scylladb#22225
f899f0e411