chore(modules-sdk): Custom Module definition (#7315)

packages/core/modules-sdk/src/loaders/__tests__/register-modules.ts

@@ -16,7 +16,6 @@ describe("module definitions loader", () => {
     registrationName: "testService",
     defaultPackage: "@medusajs/test-service",
     label: "TestService",
-    isLegacy: true,
     isRequired: false,
     defaultModuleDeclaration: {
       scope: MODULE_SCOPE.INTERNAL,

packages/core/modules-sdk/src/loaders/module-loader.ts

@@ -55,6 +55,13 @@ async function loadModule(
   loaderOnly?: boolean
 ): Promise<{ error?: Error } | void> {
   const modDefinition = resolution.definition
+
+  if (!modDefinition.key) {
+    throw new Error(`Module definition is missing property "key"`)
+  }
+
+  modDefinition.registrationName ??= modDefinition.key
+
   const registrationName = modDefinition.registrationName
 
   const { scope, resources } = resolution.moduleDeclaration ?? ({} as any)