Add GroupChatProcessor callback

Sources/ElixxirDAppsSDK/Callbacks/GroupChatProcessor.swift

+import Bindings
+import XCTestDynamicOverlay
+
+public struct GroupChatProcessor {
+  public struct Callback: Equatable {
+    public init(
+      decryptedMessage: Result<Data, NSError>,
+      msg: Data,
+      receptionId: Data,
+      ephemeralId: Int64,
+      roundId: Int64
+    ) {
+      self.decryptedMessage = decryptedMessage
+      self.msg = msg
+      self.receptionId = receptionId
+      self.ephemeralId = ephemeralId
+      self.roundId = roundId
+    }
+
+    public var decryptedMessage: Result<Data, NSError>
+    public var msg: Data
+    public var receptionId: Data
+    public var ephemeralId: Int64
+    public var roundId: Int64
+  }
+
+  public init(
+    name: String = "GroupChatProcessor",
+    handle: @escaping (Callback) -> Void
+  ) {
+    self.name = name
+    self.handle = handle
+  }
+
+  public var name: String
+  public var handle: (Callback) -> Void
+}
+
+extension GroupChatProcessor {
+  public static let unimplemented = GroupChatProcessor(
+    name: "GroupChatProcessor.unimplemented",
+    handle: XCTUnimplemented("\(Self.self)")
+  )
+}
+
+extension GroupChatProcessor {
+  func makeBindingsGroupChatProcessor() -> BindingsGroupChatProcessorProtocol {
+    class CallbackObject: NSObject, BindingsGroupChatProcessorProtocol {
+      init(_ callback: GroupChatProcessor) {
+        self.callback = callback
+      }
+
+      let callback: GroupChatProcessor
+
+      func process(
+        _ decryptedMessage: Data?,
+        msg: Data?,
+        receptionId: Data?,
+        ephemeralId: Int64,
+        roundId: Int64,
+        err: Error?
+      ) {
+        guard let msg = msg else {
+          fatalError("BindingsGroupChatProcessor received `nil` msg")
+        }
+        guard let receptionId = receptionId else {
+          fatalError("BindingsGroupChatProcessor received `nil` receptionId")
+        }
+        let decryptedMessageResult: Result<Data, NSError>
+        if let err = err {
+          decryptedMessageResult = .failure(err as NSError)
+        } else if let decryptedMessage = decryptedMessage {
+          decryptedMessageResult = .success(decryptedMessage)
+        } else {
+          fatalError("BindingsGroupChatProcessor received `nil` decryptedMessage and `nil` error")
+        }
+        callback.handle(.init(
+          decryptedMessage: decryptedMessageResult,
+          msg: msg,
+          receptionId: receptionId,
+          ephemeralId: ephemeralId,
+          roundId: roundId
+        ))
+      }
+
+      func string() -> String {
+        callback.name
+      }
+    }
+
+    return CallbackObject(self)
+  }
+}