Legal holds, step 1: the hold itself

inbuxa:LegalHold get/set places a hold on accounts, groups, domains,
tenants or the whole server, with an optional date range. A hold's range
and scope can only widen, a released hold is read-only, and none is ever
deleted. Placing, changing and releasing each need a reason and are
audited (LH-1, LH-3, LH-10, AU-12).

Permissions 669-672 (see, place, widen or release, export held data)
go to server administrators only; the tenant ceiling always strips them,
as it does Impersonate (LH-13). Schema: Compliance > Legal Holds.

What a hold keeps comes next, through the undelete hooks.

Also moves the lock expiry helpers below the lock module's imports.

crates/jmap/src/changes/get.rs

@@ -424,6 +424,7 @@ impl IntermediateChangesResponse {
             | MethodObject::AuditExport
             | MethodObject::AuditVerification
             | MethodObject::AccountLock
+            | MethodObject::LegalHold
             | MethodObject::ProtocolPolicy
             | MethodObject::TenantProtocolPolicy
             | MethodObject::Registry(_) => unreachable!(),