(MODULES-3804) Fix sort order of pg_hba_rule entries

[olavmrk]

The $order-parameter to pg_hba_rule can be either an integer or a
string, but the corresponding concat-resource is configured to sort
the entries using alphanumeric sort.

The result is that a pg_hba_rule entry with order => 2 sorts after
an entry with order => 10.

This is also a problem with the default pg_hba_rule entries, which
uses numeric order values 1, 2, 3, 4, 100 and 101. These are sorted in
the incorrect order (1, 100, 101, 2, 3, 4).

Unfortunately, since string values are allowed in the
$order-parameter, we cannot simply change the concat-resource to
use numeric sort.

This patch fixes this issue by zero-padding all integer values to
three digits. E.g. 1 becomes 001, and 10 becomes 010. This should
work well for integer values from 0 through 999, and works well with
earlier versions of the module which used string values in that range
for the $order-parameter.

[david22swan]

@olavmrk This looks like a good change that I would be happy to merge, but first could you update the documentation to mention the zero padding please?

[olavmrk]

@david22swan: I have now updated the documentation for the order parameter. I now reads:

order

Sets an order for placing the rule in pg_hba.conf.

This can be either a string or an integer. If it is an integer, it will be converted to a string by zero-padding it to three digits. E.g. 42 will be zero-padded to the string '042'.

The pg_hba_rule fragments are sorted using the alpha sorting order.

Default value: 150.

[david22swan]

@olavmrk Look's good to me. Thanks for putting in the work. :)