Bug: Precedence Operator

[independentid]

Precedence (brackets) seem to be ignored when parsing a filter like (ignore the non scim attributes):
expression := "( username eq \"test\" or request.path sw \"/finance\" ) and subject eq \"abc\""

Calling filter.ParseFilter([]byte(expression)) returns a filter.Expression result whose string value is:
username eq "test" or request.path sw "/finance" and subject eq "abc"

I have tried having spaces between brackets ("(") and content as well as no spaces.

I notice that the test does not actually validate the result, it just tests for no detected errors.

[q-uint]

This is a real bug in the String() method: the AST correctly preserves precedence, but LogicalExpression.String() always emits left op right without parentheses, so (A or B) and C prints as A or B and C, which has different semantics.

The fix belongs in LogicalExpression.String(): it should emit parentheses around a child when it's a LogicalExpression with lower precedence than the parent (i.e., an or nested inside an and). No new AST node is needed.