Use an AppStoreConnect API key instead of username:password for alpha builds

fastlane/Fastfile

@@ -19,6 +19,12 @@ lane :alpha do
     code_sign_identity: code_signing_identity
   )
 
+  app_store_connect_api_key(
+    key_id: ENV["APPSTORECONNECT_KEY_ID"],
+    issuer_id: ENV["APPSTORECONNECT_KEY_ISSUER_ID"],
+    key_content: ENV["APPSTORECONNECT_KEY_CONTENT"]
+  )
+
   get_provisioning_profile(
     app_identifier: bundle_identifier,
     provisioning_name: provisioning_profile_name,