feat: Allow customer metadata update (#9780)

* Allow customer metadata update 

See issue 9779
https://github.com/medusajs/medusa/issues/9779

* add integration tests for customer metadata

- Implemented integration tests to verify customer creation with metadata.

packages/medusa/src/api/store/customers/validators.ts

@@ -10,6 +10,7 @@ export const StoreCreateCustomer = z.object({
   first_name: z.string().nullish(),
   last_name: z.string().nullish(),
   phone: z.string().nullish(),
+  metadata: z.record(z.unknown()).nullish(),
 })
 
 export const StoreUpdateCustomer = z.object({
@@ -17,6 +18,7 @@ export const StoreUpdateCustomer = z.object({
   first_name: z.string().nullish(),
   last_name: z.string().nullish(),
   phone: z.string().nullish(),
+  metadata: z.record(z.unknown()).nullish(),
 })
 
 export const StoreGetCustomerAddressParams = createSelectParams()