[airbnb] Fix missing "Foundation" imports

Sources/Apollo/Decoding.swift

@@ -1,3 +1,5 @@
+import Foundation
+
 private typealias GroupedFields = GroupedSequence<String, GraphQLField>
 
 func decode<SelectionSet: GraphQLSelectionSet>(selectionSet: SelectionSet.Type, from object: JSONObject, variables: GraphQLMap? = nil) throws -> SelectionSet {

Sources/Apollo/GraphQLExecutor.swift

@@ -1,4 +1,5 @@
 import Dispatch
+import Foundation
 
 /// A resolver is responsible for resolving a value for a field.
 typealias GraphQLResolver = (_ object: JSONObject, _ info: GraphQLResolveInfo) -> ResultOrPromise<JSONValue?>

Sources/Apollo/GraphQLHTTPRequestError.swift

@@ -1,3 +1,5 @@
+import Foundation
+
 /// An error which has occurred during the serialization of a request.
 public enum GraphQLHTTPRequestError: Error, LocalizedError {
   case cancelledByDelegate

Sources/Apollo/GraphQLHTTPResponseError.swift

@@ -1,3 +1,5 @@
+import Foundation
+
 /// A transport-level, HTTP-specific error.
 public struct GraphQLHTTPResponseError: Error, LocalizedError {
   public enum ErrorKind {

Sources/ApolloWebSocket/WebSocketTransport.swift

@@ -2,6 +2,7 @@
 import Apollo
 #endif
 import Starscream
+import Foundation
 
 // To allow for alternative implementations supporting the same WebSocketClient protocol
 public class ApolloWebSocket: WebSocket, ApolloWebSocketClient {