Arvados

In #13996 apiserver started getting its database config from the cluster config file (Clusters.zzzzz.PostgreSQL.Connection.*).

However, it tries to use mixed-case keys like "DBName", instead of the lowercase keys like "dbname" that admins have been instructed to use in their config files. Mixed- and lower-case keys don't get merged properly, so existing config files don't work.

Propose to fix this by using lowercase keys in the apiserver code and example config.

(These keyvalues are intended to be sent directly to postgresql, whose docs write them in lowercase with no mention of automatic case flattening.)