feat: add event kind blacklist

Adds a list to the config where you can specify which event kinds to blacklist.
The blacklist check will run right after verifying that the pubkey is allowed
to post events to the relay.

src/db.rs

@@ -232,6 +232,24 @@ pub async fn db_writer(
                 }
             }
 
+            // Check that event kind isn't blacklisted
+            let kinds_blacklist = &settings.limits.event_kind_blacklist.clone();
+            if let Some(event_kind_blacklist) = kinds_blacklist {
+                if event_kind_blacklist.contains(&event.kind) {
+                    info!(
+                        "Rejecting event {}, blacklisted kind",
+                        &event.get_event_id_prefix()
+                    );
+                    notice_tx
+                        .try_send(Notice::blocked(
+                            event.id,
+                            "event kind is blocked by relay"
+                        ))
+                        .ok();
+                    continue;
+                }
+            }
+
             // send any metadata events to the NIP-05 verifier
             if nip05_active && event.is_kind_metadata() {
                 // we are sending this prior to even deciding if we
@@ -901,4 +919,4 @@ pub async fn db_query(
         let ok: Result<()> = Ok(());
         ok
     });
-}
+}