Set name_sep for default SQL::Abstract to help disambiguate columns

[Epiphero]

When using SQL::Abstract with multiple tables, it is sometimes necessary to disambiguate columns:

$pg->db->select(['foo', 'bar'], ['foo.id'], {'foo.id', => {-ident => 'bar.id'}});

If SQL::Abstract does not have a name_sep specified, it will attempt to quote the entire table-field name as "foo.id" and "bar.id" rather than "foo"."id" and "bar"."id", producing an error such as:

DBD::Pg::st execute failed: ERROR:  column "foo.id" does not exist
LINE 1: SELECT "foo.id" FROM "foo", "bar" WHERE ( "foo.id" = "bar.id...
               ^ at lib/Test.pm line 50.

The workaround is to create the Mojo::Pg instance with:

    $pg = Mojo::Pg
      ->new($db_uri)
      ->abstract(SQL::Abstract->new(quote_char => '"', name_sep => '.'))
      ;

However, since the name_sep and quote_char values are intrinsic to Postgres, it makes sense for these to be the setting on the default SQL::Abstract object.

[kraih]

Thank you, applied with tests and documentation.