domain crate code quality cleanup

strip all comments, extract tests to tests/ dirs,
remove #[allow(clippy::...)], extract magic numbers to
constants, refactor schedule engine private methods to
use param structs, add Default impls, clippy.toml for
persistence constructors

crates/domain/src/events/tests/mod.rs

@@ -0,0 +1,83 @@
+use super::*;
+use uuid::Uuid;
+
+#[test]
+fn broadcast_transition_carries_ids() {
+    let ch = ChannelId::from(Uuid::new_v4());
+    let sl = SlotId::from(Uuid::new_v4());
+    let event = DomainEvent::BroadcastTransition {
+        channel_id: ch,
+        slot_id: sl,
+    };
+    match event {
+        DomainEvent::BroadcastTransition {
+            channel_id,
+            slot_id,
+        } => {
+            assert_eq!(channel_id, ch);
+            assert_eq!(slot_id, sl);
+        }
+        _ => panic!("wrong variant"),
+    }
+}
+
+#[test]
+fn no_signal_carries_channel_id() {
+    let ch = ChannelId::from(Uuid::new_v4());
+    let event = DomainEvent::NoSignal { channel_id: ch };
+    match event {
+        DomainEvent::NoSignal { channel_id } => assert_eq!(channel_id, ch),
+        _ => panic!("wrong variant"),
+    }
+}
+
+#[test]
+fn schedule_generated_carries_ids() {
+    let ch = ChannelId::from(Uuid::new_v4());
+    let sc = ScheduleId::from(Uuid::new_v4());
+    let event = DomainEvent::ScheduleGenerated {
+        channel_id: ch,
+        schedule_id: sc,
+    };
+    match event {
+        DomainEvent::ScheduleGenerated {
+            channel_id,
+            schedule_id,
+        } => {
+            assert_eq!(channel_id, ch);
+            assert_eq!(schedule_id, sc);
+        }
+        _ => panic!("wrong variant"),
+    }
+}
+
+#[test]
+fn channel_lifecycle_events() {
+    let ch = ChannelId::from(Uuid::new_v4());
+
+    let created = DomainEvent::ChannelCreated { channel_id: ch };
+    let updated = DomainEvent::ChannelUpdated { channel_id: ch };
+    let deleted = DomainEvent::ChannelDeleted { channel_id: ch };
+
+    for event in [created, updated, deleted] {
+        match event {
+            DomainEvent::ChannelCreated { channel_id }
+            | DomainEvent::ChannelUpdated { channel_id }
+            | DomainEvent::ChannelDeleted { channel_id } => {
+                assert_eq!(channel_id, ch);
+            }
+            _ => panic!("wrong variant"),
+        }
+    }
+}
+
+#[test]
+fn event_is_clone() {
+    let ch = ChannelId::from(Uuid::new_v4());
+    let event = DomainEvent::NoSignal { channel_id: ch };
+    let cloned = event.clone();
+    match cloned {
+        DomainEvent::NoSignal { channel_id } => assert_eq!(channel_id, ch),
+        _ => panic!("wrong variant"),
+    }
+}