fix(patch): [sc-14974] make kafka metadata sendable (#45)

Sources/Kafka/KafkaMetadata.swift

@@ -1,54 +1,29 @@
 import Crdkafka
 
-public final class KafkaMetadata {
-    private let metadata: UnsafePointer<rd_kafka_metadata>
-    
+public struct KafkaMetadata: Sendable {
+    public let topics: [KafkaTopicMetadata]
+
     init(metadata: UnsafePointer<rd_kafka_metadata>) {
-        self.metadata = metadata
-    }
-
-    deinit {
-        rd_kafka_metadata_destroy(metadata)
+        self.topics = (0..<Int(metadata.pointee.topic_cnt)).map { KafkaTopicMetadata(topic: metadata.pointee.topics[$0]) }
     }
-
-    public private(set) lazy var topics = {
-        (0..<Int(self.metadata.pointee.topic_cnt)).map { KafkaTopicMetadata(metadata: self, topic: self.metadata.pointee.topics[$0]) }
-    }()
 }
 
-// must be a class to allow mutating lazy vars, otherwise require struct copies
-public final class KafkaTopicMetadata {
-    private let metadata: KafkaMetadata // retain metadata
-    private let topic: rd_kafka_metadata_topic
-
-    init(metadata: KafkaMetadata, topic: rd_kafka_metadata_topic) {
-        self.metadata = metadata
-        self.topic = topic
-    }
+public struct KafkaTopicMetadata: Sendable {
+    public let name: String
+    public let partitions: [KafkaPartitionMetadata]
 
-    public private(set) lazy var name = {
-        String(cString: self.topic.topic)
-    }()
-
-    public private(set) lazy var partitions = {
-        (0..<Int(self.topic.partition_cnt)).map { KafkaPartitionMetadata(metadata: self.metadata, partition: topic.partitions[$0]) }
-    }()
+    init(topic: rd_kafka_metadata_topic) {
+        self.name = String(cString: topic.topic)
+        self.partitions = (0..<Int(topic.partition_cnt)).map { KafkaPartitionMetadata( topic.partitions[$0]) }
+    }
 }
 
-public struct KafkaPartitionMetadata {
-    private let metadata: KafkaMetadata // retain metadata
-    private let partition: rd_kafka_metadata_partition
-
-    init(metadata: KafkaMetadata, partition: rd_kafka_metadata_partition) {
-        self.metadata = metadata
-        self.partition = partition
-    }
+public struct KafkaPartitionMetadata: Sendable {
+    public let id: Int
+    public let replicasCount: Int
 
-    var id: Int {
-        Int(partition.id)
-    }
-
-    var replicasCount: Int {
-        Int(partition.replica_cnt)
+    init(_ partition: rd_kafka_metadata_partition) {
+        self.id = Int(partition.id)
+        self.replicasCount = Int(partition.replica_cnt)
     }
 }