Fix user discovery search

• Add UDSearchResult model.
• Use UDSearchResult model in UdSearchCallback.
• Workaround: Convert big ints in UdSearchResult JSON to strings.

Sources/XXClient/Models/UDSearchResult.swift

+import Foundation
+
+public struct UDSearchResult: Equatable {
+  public init(
+    id: Data,
+    facts: [Fact]
+  ) {
+    self.id = id
+    self.facts = facts
+  }
+
+  public var id: Data
+  public var facts: [Fact]
+}
+
+extension UDSearchResult: Codable {
+  enum CodingKeys: String, CodingKey {
+    case id = "ID"
+    case facts = "Facts"
+  }
+
+  public static func decode(_ data: Data) throws -> Self {
+    try JSONDecoder().decode(Self.self, from: data)
+  }
+
+  public func encode() throws -> Data {
+    try JSONEncoder().encode(self)
+  }
+}
+
+extension Array where Element == UDSearchResult {
+  public static func decode(_ data: Data) throws -> Self {
+    try JSONDecoder().decode(Self.self, from: data)
+  }
+
+  public func encode() throws -> Data {
+    try JSONEncoder().encode(self)
+  }
+}