Implement MSC4028: push all encrypted events. (#16361)

This unstable push rule is implemented behind an experimental
configuration flag.

rust/src/push/base_rules.rs

@@ -63,6 +63,19 @@ pub const BASE_PREPEND_OVERRIDE_RULES: &[PushRule] = &[PushRule {
 }];
 
 pub const BASE_APPEND_OVERRIDE_RULES: &[PushRule] = &[
+    PushRule {
+        rule_id: Cow::Borrowed("global/override/.org.matrix.msc4028.encrypted_event"),
+        priority_class: 5,
+        conditions: Cow::Borrowed(&[Condition::Known(KnownCondition::EventMatch(
+            EventMatchCondition {
+                key: Cow::Borrowed("type"),
+                pattern: Cow::Borrowed("m.room.encrypted"),
+            },
+        ))]),
+        actions: Cow::Borrowed(&[Action::Notify]),
+        default: true,
+        default_enabled: false,
+    },
     PushRule {
         rule_id: Cow::Borrowed("global/override/.m.rule.suppress_notices"),
         priority_class: 5,

rust/src/push/evaluator.rs

@@ -564,7 +564,7 @@ fn test_requires_room_version_supports_condition() {
     };
     let rules = PushRules::new(vec![custom_rule]);
     result = evaluator.run(
-        &FilteredPushRules::py_new(rules, BTreeMap::new(), true, false, true),
+        &FilteredPushRules::py_new(rules, BTreeMap::new(), true, false, true, false),
         None,
         None,
     );

rust/src/push/mod.rs

@@ -527,6 +527,7 @@ pub struct FilteredPushRules {
     msc1767_enabled: bool,
     msc3381_polls_enabled: bool,
     msc3664_enabled: bool,
+    msc4028_push_encrypted_events: bool,
 }
 
 #[pymethods]
@@ -538,6 +539,7 @@ impl FilteredPushRules {
         msc1767_enabled: bool,
         msc3381_polls_enabled: bool,
         msc3664_enabled: bool,
+        msc4028_push_encrypted_events: bool,
     ) -> Self {
         Self {
             push_rules,
@@ -545,6 +547,7 @@ impl FilteredPushRules {
             msc1767_enabled,
             msc3381_polls_enabled,
             msc3664_enabled,
+            msc4028_push_encrypted_events,
         }
     }
 
@@ -581,6 +584,12 @@ impl FilteredPushRules {
                     return false;
                 }
 
+                if !self.msc4028_push_encrypted_events
+                    && rule.rule_id == "global/override/.org.matrix.msc4028.encrypted_event"
+                {
+                    return false;
+                }
+
                 true
             })
             .map(|r| {