Allowing usernames in pg_hba.conf

We have the following TODO item:
* Allow usernames to be specified directly in pg_hba.conf (Bruce)

My idea is to allow comma-separated usernames in the AUTH_ARGUMENT
column.  Right now we use it for ident user map files and secondary
password files.  It seems both easily already allow username
restrictions.  Adding usernames directly in pg_hba.conf is basically a
shortcut to creating such secondary files.

My idea is that if AUTH_ARGUMENT starts with "=", it represents a list
of comma-separated usernames.
 host       template1   192.168.12.10 255.255.255.255    md5 =bmomjian,jeffw

Do I need to allow usernames with spaces or quoted usernames?  I don't
think so.

For implementation, I was going to simulate a secondary password file
with no passwords.  We already support that internally as a username
restriction option. Those are loaded into memory as linked lists of text
lines, if I remember correclty.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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