// ParseDateTimeTZ attempts to parse the given date string from multiple formats.
// First, a time-zoned date-time string (e.g. 2006-01-02T15:04:05+02:00) is tried
// Second, a non-time-zoned date-time string (e.g. 2006-01-02 15:04:05) is tried at the given zone
// Third, a non-time-zoned date string (e.g. 2006-01-02) is tried at the given zone
// Example:
// - Server runs in CEST (UTC+2), requesting user lives in PDT (UTC-7).
// - 2021-04-25T10:30:00Z, 2021-04-25T3:30:00-0100 and 2021-04-25T12:30:00+0200 are equivalent, they represent the same point in time
// - When user requests non-time-zoned range (e.g. 2021-04-25T00:00:00), but has their time zone properly configured, this will resolve to 2021-04-25T09:00:00