DLP: how long held mail waits is a setting

inbuxa:DlpSettings (singleton, urn:inbuxa:jmap): keepHeldDays, 1 to 90,
7 by default (settled answer 5 made it a setting). sysDlpPolicyGet reads
it, sysDlpPolicyUpdate changes it, server-level, audited by the request
layer. Each held message keeps the days it was given, and the sender's
notices say that number. Privacy catalog entry; spec §2.6 updated.

mail_rules_tests: 7 by default, 0 refused, 3 set and a message held
afterwards expires 3 days after it was held, the expiry notice says 3.

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

@@ -50,6 +50,7 @@ pub enum MethodObject {
     // inbuxa: AI call limits
     AiLimits,
     LogSettings,
+    DlpSettings,
     DataInventory,
     InventorySnapshot,
     // inbuxa: "Explain this" with the local model
@@ -96,6 +97,7 @@ impl MethodObject {
             MethodObject::DeletedAccount => Capability::Inbuxa,
             MethodObject::AiLimits => Capability::Inbuxa,
             MethodObject::LogSettings => Capability::Inbuxa,
+            MethodObject::DlpSettings => Capability::Inbuxa,
             MethodObject::DataInventory => Capability::Inbuxa,
             MethodObject::InventorySnapshot => Capability::Inbuxa,
             MethodObject::Explanation => Capability::Inbuxa,
@@ -288,9 +290,11 @@ impl MethodName {
             (MethodFunction::Get, MethodObject::AiLimits) => "inbuxa:AiLimits/get",
             (MethodFunction::Set, MethodObject::AiLimits) => "inbuxa:AiLimits/set",
             (MethodFunction::Get, MethodObject::LogSettings) => "inbuxa:LogSettings/get",
+            (MethodFunction::Get, MethodObject::DlpSettings) => "inbuxa:DlpSettings/get",
             (MethodFunction::Get, MethodObject::DataInventory) => "inbuxa:DataInventory/get",
             (MethodFunction::Get, MethodObject::InventorySnapshot) => "inbuxa:InventorySnapshot/get",
             (MethodFunction::Set, MethodObject::LogSettings) => "inbuxa:LogSettings/set",
+            (MethodFunction::Set, MethodObject::DlpSettings) => "inbuxa:DlpSettings/set",
             (MethodFunction::Set, MethodObject::Explanation) => "inbuxa:Explanation/set",
             (MethodFunction::Get, MethodObject::AuditEvent) => "inbuxa:AuditEvent/get",
             (MethodFunction::Query, MethodObject::AuditEvent) => "inbuxa:AuditEvent/query",
@@ -444,9 +448,11 @@ impl MethodName {
             "inbuxa:AiLimits/get" => (MethodObject::AiLimits, MethodFunction::Get),
             "inbuxa:AiLimits/set" => (MethodObject::AiLimits, MethodFunction::Set),
             "inbuxa:LogSettings/get" => (MethodObject::LogSettings, MethodFunction::Get),
+            "inbuxa:DlpSettings/get" => (MethodObject::DlpSettings, MethodFunction::Get),
             "inbuxa:DataInventory/get" => (MethodObject::DataInventory, MethodFunction::Get),
             "inbuxa:InventorySnapshot/get" => (MethodObject::InventorySnapshot, MethodFunction::Get),
             "inbuxa:LogSettings/set" => (MethodObject::LogSettings, MethodFunction::Set),
+            "inbuxa:DlpSettings/set" => (MethodObject::DlpSettings, MethodFunction::Set),
             "inbuxa:Explanation/set" => (MethodObject::Explanation, MethodFunction::Set),
             "inbuxa:AuditEvent/get" => (MethodObject::AuditEvent, MethodFunction::Get),
             "inbuxa:AuditEvent/query" => (MethodObject::AuditEvent, MethodFunction::Query),
@@ -522,6 +528,7 @@ impl Display for MethodObject {
             MethodObject::DeletedAccount => "inbuxa:DeletedAccount",
             MethodObject::AiLimits => "inbuxa:AiLimits",
             MethodObject::LogSettings => "inbuxa:LogSettings",
+            MethodObject::DlpSettings => "inbuxa:DlpSettings",
             MethodObject::DataInventory => "inbuxa:DataInventory",
             MethodObject::InventorySnapshot => "inbuxa:InventorySnapshot",
             MethodObject::Explanation => "inbuxa:Explanation",