Servers: Fix create / leave.

Prevent removal of self / owner.

src/routes/servers/member_remove.rs

@@ -21,5 +21,9 @@ pub async fn req(user: User, target: Ref, member: String) -> Result<()> {
         return Err(Error::InvalidOperation)
     }
 
+    if target.id == target.owner {
+        return Err(Error::MissingPermission)
+    }
+
     target.remove_member(&member.id.user).await
 }