nostr: add RelayMetadata::Discovery variant

Signed-off-by: Yuki Kishimoto <[email protected]>

crates/nostr/src/event/tag.rs

@@ -330,13 +330,16 @@ pub enum RelayMetadata {
     Read,
     /// Write
     Write,
+    /// Discovery
+    Discovery,
 }
 
 impl fmt::Display for RelayMetadata {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::Read => write!(f, "read"),
             Self::Write => write!(f, "write"),
+            Self::Discovery => write!(f, "discovery"),
         }
     }
 }
@@ -348,6 +351,7 @@ impl FromStr for RelayMetadata {
         match s {
             "read" => Ok(Self::Read),
             "write" => Ok(Self::Write),
+            "discovery" => Ok(Self::Discovery),
             s => Err(Error::InvalidRelayMetadata(s.to_string())),
         }
     }