The display name shown in the directory + on calendar invites.
The mailbox local part (mailNickname) derived from the address.
OptionalTenantThe Azure tenant id the mailbox is created in, when supplied via request Configuration.TenantId.
OptionalUsageThe directory OU/usage-location hint, when supplied via request Configuration.UsageLocation.
The mailbox UPN/address to create (user.userPrincipalName + mailNickname).
The Microsoft Graph
POST /userscreate-mailbox payload (the subset we construct).