addding an NLOHMANN_DEFINE_TYPE_READONLY macro

[e2sn4uudk]

This additional macro allows easy serialization of objects with const members, and sometimes serialization is all a project needs (https://github.com/karlkurzer/json/pull/1/commits/7ecc6fdb52072bc30fdfeb3391cd0bf27fe4b317)

What do you think? Or does that already exist and I just haven't seen it?

[nlohmann]

No NLOHMANN_DEFINE_TYPE_READONLY-style macro exists in the current macro set — the existing macros all generate a from_json that assigns directly to member variables via get_to, which requires non-const, assignable members. Supporting const members would need a constructor-based from_json (returning a newly constructed Type rather than mutating one in place), which is a reasonable and fairly self-contained addition for types that only need serialization plus immutable construction.

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This reply was drafted by Claude Code on behalf of @nlohmann, as part of a review of open discussions.

[gregmarr]

@nlohmann I don't know for sure because the fork is gone, but I believe this is looking for NLOHMANN_DEFINE_TYPE_[NON_]INTRUSIVE_ONLY_SERIALIZE which does only to_json(), not from_json().