Use nonstandard_host_prefix

Author: jecepeda

lib/shopify_api/auth/oauth.rb

@@ -116,7 +116,7 @@ def auth_base_uri(shop)
           # For first-party apps in development only, we leverage DevServer to build the admin base URI
           admin_web = T.unsafe(Object.const_get("DevServer")) # rubocop:disable Sorbet/ConstantsFromStrings
             .new("admin-web")
-          admin_host = admin_web.host!
+          admin_host = admin_web.host!(nonstandard_host_prefix: "admin")
           shop_name = shop.split(".").first
 
           "https://#{admin_host}/store/#{shop_name}"