The server supports its own notion of locale, separate from the OS locale. It's used for error messages (lc_messages server variable) and for month/weekday names (lc_time_names server variable).

This task is about expanding locales to affect numeric formatting, in style of the standard LC_NUMERIC setting. In particular:

• add lc_numeric server variable
• it should specify a thousand separator and a decimal point character
• it should affect the output of FORMAT() function and :L specifier of SFORMAT() function.