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/references/resolve.rs

@@ -41,6 +41,7 @@ impl Response<'_> {
                 GetRequestMethod::PushSubscription(request) => request.resolve_references(self)?,
                 GetRequestMethod::Sieve(request) => request.resolve_references(self)?,
                 GetRequestMethod::VacationResponse(request) => request.resolve_references(self)?,
+                GetRequestMethod::MaskedEmail(request) => request.resolve_references(self)?,
                 GetRequestMethod::Principal(request) => request.resolve_references(self)?,
                 GetRequestMethod::Quota(request) => request.resolve_references(self)?,
                 GetRequestMethod::Blob(request) => request.resolve_references(self)?,
@@ -75,6 +76,9 @@ impl Response<'_> {
                 SetRequestMethod::VacationResponse(request) => {
                     request.resolve_references(self, 1, false)?
                 }
+                SetRequestMethod::MaskedEmail(request) => {
+                    request.resolve_references(self, 1, false)?
+                }
                 SetRequestMethod::AddressBook(request) => {
                     request.resolve_references(self, 1, false)?
                 }