Query and set seen status via store

src/euph/small_message.rs

@@ -94,6 +94,7 @@ pub struct SmallMessage {
     pub time: Time,
     pub nick: String,
     pub content: String,
+    pub seen: bool,
 }
 
 fn as_me(content: &str) -> Option<&str> {
@@ -144,6 +145,10 @@ impl Msg for SmallMessage {
         self.parent
     }
 
+    fn seen(&self) -> bool {
+        self.seen
+    }
+
     fn last_possible_id() -> Self::Id {
         Snowflake::MAX
     }