add createNewsletterEmailPublisher

apple/OmnivoreKit/Sources/Services/DataService/Mutations/CreateNewsletterEmailMutation.swift

@@ -0,0 +1,60 @@
+import Combine
+import Foundation
+import Models
+import SwiftGraphQL
+
+public extension DataService {
+  func createNewsletterEmailPublisher() -> AnyPublisher<NewsletterEmail, BasicError> {
+    enum MutationResult {
+      case saved(newsletterEmail: NewsletterEmail)
+      case error(errorCode: Enums.CreateNewsletterEmailErrorCode)
+    }
+
+    let selection = Selection<MutationResult, Unions.CreateNewsletterEmailResult> {
+      try $0.on(
+        createNewsletterEmailSuccess: .init {
+          .saved(newsletterEmail: try $0.newsletterEmail(selection: Selection.NewsletterEmail {
+            NewsletterEmail(
+              emailId: try $0.id(),
+              email: try $0.address(),
+              confirmationCode: try $0.confirmationCode()
+            )
+          }))
+        }, createNewsletterEmailError: .init {
+          .error(errorCode: try $0.errorCodes().first ?? .badRequest)
+        }
+      )
+    }
+
+    let mutation = Selection.Mutation {
+      try $0.createNewsletterEmail(selection: selection)
+    }
+
+    let path = appEnvironment.graphqlPath
+    let headers = networker.defaultHeaders
+
+    return Deferred {
+      Future { promise in
+        send(mutation, to: path, headers: headers) { result in
+          switch result {
+          case let .success(payload):
+            if let graphqlError = payload.errors {
+              promise(.failure(.message(messageText: "graphql error: \(graphqlError)")))
+            }
+
+            switch payload.data {
+            case let .saved(newsletterEmail: newsletterEmail):
+              promise(.success(newsletterEmail))
+            case let .error(errorCode: errorCode):
+              promise(.failure(.message(messageText: errorCode.rawValue)))
+            }
+          case .failure:
+            promise(.failure(.message(messageText: "graphql error")))
+          }
+        }
+      }
+    }
+    .receive(on: DispatchQueue.main)
+    .eraseToAnyPublisher()
+  }
+}