DERP mesh key setup would do a SELECT and then an INSERT on failure, without a lock. During some testing with multiple replicas, I managed to cause a replica to crash due to them initializing simultaneously.
Fixes:
Encountered an error running "coder server"
create coder API: insert mesh key: pq: duplicate key value violates unique constraint "site_configs_key_key"
Co-authored-by: Cian Johnston <cian@coder.com>
