The identifier is known only to the DOI registration agency.
This status may be used to reserve an identifier name without advertising the identifier's existence
to resolvers and other external services.
A reserved identifier may be fully deleted.
The identifier once was registered, but the object referenced by the identifier is not available.
This is known as an "inactive" DOI in DataCite and "unavailable" in EZID.
In EZID the identifier redirects to an EZID-provided "tombstone" page regardless of its target URL.
In DataCite the original target URL is still available.
Returns the enum constant of this type with the specified name.
The string must match exactly an identifier used to declare an
enum constant in this type. (Extraneous whitespace characters are
name - the name of the enum constant to be returned.