Update Jetpack connection for flow from login

Author: itsmeichigo

WooCommerce/Classes/Authentication/Jetpack Setup/LoginJetpackSetupCoordinator.swift

@@ -44,7 +44,11 @@ final class LoginJetpackSetupCoordinator: Coordinator {
 //
 private extension LoginJetpackSetupCoordinator {
     func showSetupSteps() {
-        let setupUI = JetpackSetupHostingController(siteURL: siteURL, connectionOnly: connectionOnly, onStoreNavigation: { [weak self] connectedEmail in
+        let setupUI = JetpackSetupHostingController(
+            siteURL: siteURL,
+            connectionOnly: connectionOnly,
+            wpcomCredentials: stores.sessionManager.defaultCredentials,
+            onStoreNavigation: { [weak self] connectedEmail in
             guard let self, let email = connectedEmail else { return }
             if email != self.stores.sessionManager.defaultAccount?.email {
                 // if the user authorized Jetpack with a different account, support them to log in with that account.

WooCommerce/Classes/Authentication/Jetpack Setup/Native Jetpack Setup/JetpackSetupView.swift

@@ -11,7 +11,7 @@ final class JetpackSetupHostingController: UIHostingController<JetpackSetupView>
 
     init(siteURL: String,
          connectionOnly: Bool,
-         wpcomCredentials: Credentials? = nil,
+         wpcomCredentials: Credentials?,
          stores: StoresManager = ServiceLocator.stores,
          authentication: Authentication = ServiceLocator.authenticationManager,
          analytics: Analytics = ServiceLocator.analytics,

WooCommerce/Classes/Authentication/Jetpack Setup/Native Jetpack Setup/JetpackSetupViewModel.swift

@@ -450,8 +450,10 @@ private extension JetpackSetupViewModel {
     }
 
     func finalizeSiteConnection(blogID: Int64, provisionResponse: JetpackConnectionProvisionResponse) {
-        guard let wpcomCredentials else {
-            return // TODO: what now?
+        guard let wpcomCredentials, case .wpcom = wpcomCredentials else {
+            /// WPCom credentials are necessary to finalize connection through API
+            /// If this is unavailable, fall back to the web flow.
+            return fetchJetpackConnectionURL()
         }
         let network = AlamofireNetwork(credentials: wpcomCredentials)
         stores.dispatch(JetpackConnectionAction.finalizeConnection(