Don't require C++17 for this change (yet!)

15 jobs for unused_keys in 21 minutes and 4 seconds (queued for 1 second)
Status Job ID Name Coverage
  Compilation
passed cmp:cc7-docker #16295427
docker

00:06:40

passed cmp:cc7-gcc #16295425
docker

00:03:46

passed cmp:cc7-llvm #16295428
docker

00:02:45

passed cmp:cc8-gcc #16295424
docker

00:02:24

passed cmp:lxplus-gcc #16295426
docker

00:03:25

passed cmp:mac1015-clang #16295429
mac

00:03:25

 
  Testing
passed tst:align #16295431
docker

00:06:26

passed tst:io #16295432
docker

00:02:21

passed tst:sim #16295433
docker

00:00:16

passed tst:tracking #16295430
docker

00:05:47

 
  Formatting
passed fmt:cc7-llvm-lint #16295435
docker

00:21:00

passed fmt:centos7-llvm-format #16295434
docker

00:00:29

passed fmt:codespell #16295436
docker

00:00:13

 
  Documentation
passed cmp:doxygen #16295437
docker

00:00:26

passed cmp:usermanual #16295438
docker

00:00:45