Serialize multiple name-value collections into a flat json object

[alluettiv]

I have a structure like this:

struct PROPS
{
    unordered_map<int, string> Keyed;
    unordered_map<string, string> Named;
};
constexpr string_view GetKeyName(int key);

struct REPORT
{
    PROPS Sess;
    PROPS Trans;
};
REPORT GetReport();

I can't merge Keyed and Named members into a single collection due to performance penalty. And I can't merge Sess and Trans members because items in Sess remain unchanged, while items in Trans are cleared on every transaction.
Now I have to serialize all properties from both objects and collections into a flat list of name-value pairs of a single json object:
Below is the linear iteration that generates each pair, but I don't know how to express serialization rules/representation in Glaze API.

auto rep = GetReport();

for (const auto& [n, v] : rep.Sess.Named)
    write_json_property(n, v);
for (const auto& [k, v] : rep.Sess.Keyed)
    write_json_property(GetKeyName(k), v);

for (const auto& [n, v] : rep.Trans.Named)
    write_json_property(n, v);
for (const auto& [k, v] : rep.Trans.Keyed)
    write_json_property(GetKeyName(k), v);