The expression to filter campaigns.
Supported fields: status, updated_at.
Key-value pairs are separated by a colon and multiple filter queries can be joined by AND/OR statements.
The boolean operators are case sensitive.
Date range filters use ISO 8601 format.
Examples:
status:active returns campaigns with status active.
status:active OR status:scheduled returns campaigns with status active or scheduled.
updated_at:[2026-01-01T00:00:00 TO *] returns campaigns modified after the given date.
updated_at:[2026-01-01T00:00:00 TO 2026-01-31T23:59:59] returns campaigns modified within the given date range.