Fail unless every non-NULL site_key is in its canonical spelling
Source: R/site_key.R
check_site_key_format.RdThe release gate for site_key_sql(): a site_key that is not equal to its own
normalisation would key a section or a climatology cell onto a station that
does not exist. NULL is allowed (underway, transect and region-pooled samples
have no station). Reports per dataset so the offending ingest is named.