CheckNameAvailabilityReason type   
Possible reasons for a name not being available. 
KnownCheckNameAvailabilityReason can be used interchangeably with CheckNameAvailabilityReason,
this enum contains the known values that the service supports.
Known values supported by the service
Invalid: Name is invalid. 
AlreadyExists: Name already exists.
type CheckNameAvailabilityReason = string