fix(tax): Make system provider registration backward compatible (#12441)

* fix(tax): Make provider registration backward compatible

* add tests

integration-tests/modules/medusa-config.js

@@ -10,6 +10,13 @@ process.env.LOG_LEVEL = "error"
 
 const enableMedusaV2 = process.env.MEDUSA_FF_MEDUSA_V2 == "true"
 
+const customTaxProviderRegistration = {
+  resolve: {
+    services: [require("@medusajs/tax/dist/providers/system").default],
+  },
+  id: "system_2",
+}
+
 const customPaymentProvider = {
   resolve: {
     services: [require("@medusajs/payment/dist/providers/system").default],
@@ -89,7 +96,12 @@ module.exports = {
     [Modules.WORKFLOW_ENGINE]: true,
     [Modules.API_KEY]: true,
     [Modules.STORE]: true,
-    [Modules.TAX]: true,
+    [Modules.TAX]: {
+      resolve: "@medusajs/tax",
+      options: {
+        providers: [customTaxProviderRegistration],
+      },
+    },
     [Modules.CURRENCY]: true,
     [Modules.ORDER]: true,
     [Modules.PAYMENT]: {