add support for nip94

quartz/src/main/java/com/vitorpamplona/quartz/events/FileHeaderEvent.kt

@@ -4,6 +4,7 @@ import androidx.compose.runtime.Immutable
 import com.vitorpamplona.quartz.utils.TimeUtils
 import com.vitorpamplona.quartz.encoders.toHexKey
 import com.vitorpamplona.quartz.crypto.CryptoUtils
+import com.vitorpamplona.quartz.crypto.KeyPair
 import com.vitorpamplona.quartz.encoders.HexKey
 
 @Immutable
@@ -53,7 +54,7 @@ class FileHeaderEvent(
             torrentInfoHash: String? = null,
             encryptionKey: AESGCM? = null,
             sensitiveContent: Boolean? = null,
-            privateKey: ByteArray,
+            keyPair: KeyPair,
             createdAt: Long = TimeUtils.now()
         ): FileHeaderEvent {
             val tags = listOfNotNull(
@@ -76,10 +77,10 @@ class FileHeaderEvent(
             )
 
             val content = description ?: ""
-            val pubKey = CryptoUtils.pubkeyCreate(privateKey).toHexKey()
+            val pubKey = keyPair.pubKey.toHexKey()
             val id = generateId(pubKey, createdAt, kind, tags, content)
-            val sig = CryptoUtils.sign(id, privateKey)
-            return FileHeaderEvent(id.toHexKey(), pubKey, createdAt, tags, content, sig.toHexKey())
+            val sig = if (keyPair.privKey == null) null else CryptoUtils.sign(id, keyPair.privKey)
+            return FileHeaderEvent(id.toHexKey(), pubKey, createdAt, tags, content, sig?.toHexKey() ?: "")
         }
     }
 }