The time until the login URL expires.
To specify expires_in set the time with a unit. The format is:
- Years to "y"
- Weeks to "w"
- Days to "d"
- Hours to "h"
- Minutes to "m"
- Seconds to "100s"
For example, "1y", "5m" or "7d".
If expires_in is set without a unit, it defaults to `seconds.