Fix compilation with nlohman_json 3.10.5

It seems the latest nlohman::json and be printed with something like fmt::print("{}", json_object), which clashes with the custom formatting we added to MessageSvcSink.cpp.

This MR wraps nlohman::json before passing it to fmtlib to disambiguate.

Closes #220 (closed)

changed milestone to %v36r5

assigned to @clemenci

added lhcb-gaudi-head label

• [2022-03-24 00:04] Validation started with lhcb-gaudi-head#3196
• [2022-03-24 00:34] Validation started with lhcb-run2-gaudi-head#295
• [2022-03-25 00:06] Validation started with lhcb-gaudi-head#3197
• [2022-03-25 00:39] Validation started with lhcb-run2-gaudi-head#296

approved this merge request

merged

mentioned in commit 3ef4ac76

mentioned in merge request atlas/Gaudi!230 (merged)

mentioned in merge request atlas/athena!51784 (merged)