netdir: more documentation on MIDDLE_ONLY flag.

Clarify that it isn't anything that most users will need to check.

crates/tor-netdoc/src/doc/netstatus.rs

@@ -467,6 +467,10 @@ bitflags! {
         const HSDIR = (1<<5);
         /// Set if this relay is considered "middle only", not suitable to run
         /// as an exit or guard relay.
+        ///
+        /// Note that this flag is only used by authorities as part of
+        /// the voting process; clients do not and should not act
+        /// based on whether it is set.
         const MIDDLE_ONLY = (1<<12);
         /// If set, there is no consensus for the ed25519 key for this relay.
         const NO_ED_CONSENSUS = (1<<6);

crates/tor-netdoc/src/doc/netstatus/rs.rs

@@ -160,6 +160,10 @@ macro_rules! implement_accessors {
                 self.rs.flags.contains(RelayFlags::HSDIR)
             }
             /// Return true if this routerstatus is listed with the MiddleOnly flag.
+            ///
+            /// Note that this flag is only used by authorities as part of
+            /// the voting process; clients do not and should not act
+            /// based on whether it is set.
             pub fn is_flagged_middle_only(&self) -> bool {
                 self.rs.flags.contains(RelayFlags::MIDDLE_ONLY)
             }