OData filter expression applied to time off requests. Supported operators: eq (equals, use eq null to match NULL), ne (not equals, use ne null to match NOT NULL), lt (less than), le (less than or equal), gt (greater than), ge (greater than or equal), in (value in list), and (combine clauses). Not supported: or, not, parenthesized grouping. Filterable fields: id, employeeId, categoryId, startDate, endDate, amount, unit, status, requestedAt. status accepts the four values of the response enum. A request that a later edit replaced is never returned by this endpoint, so no filter can select one. Examples: status eq 'approved', employeeId in (614, 615, 616), status eq 'approved' and startDate ge '2026-04-01' and endDate le '2026-05-01'.
