Masked email: Fastmail's Masked Email API, MaskedEmail/get and /set (ME-1, ME-7a, ME-16)

Advertised as https://www.fastmail.com/dev/maskedemail in the session and on
every account that may hold masks. Masks created through it start pending
unless the create sets a state; pending can't be set again once left; state
and the other mutable fields map onto the same records the x: API uses.

crates/jmap-proto/src/request/mod.rs

@@ -111,6 +111,7 @@ pub enum GetRequestMethod {
     ParticipantIdentity(Box<GetRequest<ParticipantIdentity>>),
     ShareNotification(Box<GetRequest<ShareNotification>>),
     Registry(Box<GetRequest<Registry>>),
+    MaskedEmail(Box<GetRequest<crate::object::fastmail_masked_email::FastmailMaskedEmail>>),
 }
 
 #[derive(Debug)]
@@ -131,6 +132,7 @@ pub enum SetRequestMethod<'x> {
     CalendarEventNotification(Box<SetRequest<'x, CalendarEventNotification>>),
     ParticipantIdentity(Box<SetRequest<'x, ParticipantIdentity>>),
     Registry(Box<SetRequest<'x, Registry>>),
+    MaskedEmail(Box<SetRequest<'x, crate::object::fastmail_masked_email::FastmailMaskedEmail>>),
 }
 
 #[derive(Debug)]