Prevent fetching messages from other channels. Change channel tag to channel_type.

src/routes/channels/message_delete.rs

@@ -12,7 +12,7 @@ pub async fn req(user: User, target: Ref, msg: Ref) -> Result<()> {
         Err(Error::LabelMe)?
     }
 
-    let message = msg.fetch_message().await?;
+    let message = msg.fetch_message(&channel).await?;
     if message.author != user.id && !perm.get_manage_messages() {
         match channel {
             Channel::SavedMessages { .. } => unreachable!(),

src/routes/channels/message_edit.rs

@@ -25,7 +25,7 @@ pub async fn req(user: User, target: Ref, msg: Ref, edit: Json<Data>) -> Result<
         Err(Error::LabelMe)?
     }
 
-    let message = msg.fetch_message().await?;
+    let message = msg.fetch_message(&channel).await?;
     if message.author != user.id {
         Err(Error::CannotEditMessage)?
     }

src/routes/channels/message_fetch.rs

@@ -12,6 +12,6 @@ pub async fn req(user: User, target: Ref, msg: Ref) -> Result<JsonValue> {
         Err(Error::LabelMe)?
     }
 
-    let message = msg.fetch_message().await?;
+    let message = msg.fetch_message(&channel).await?;
     Ok(json!(message))
 }