Implement db idle connections with a default SetConnMaxLifetime #262
Description
PR #261 was needed because after an idle time of >60s the next query was always failing with Query Failed - invalid connection.
The quick fix was to set the max number of idle connections to 0, but his negates the purpose of having a connection pool. We should have a reasonable default for SetConnMaxLifetime. If the connection expiration time can be configured in gitbase, maybe we should also have an option in gitbase-web.