feat(customer): add customer group management apis (#6233)

**What**
```
POST /admin/customer-groups
POST /admin/customer-groups/:id
GET /admin/customer-groups/:id
DELETE /admin/customer-groups/:id
```

- Workflows

packages/medusa/src/api-v2/admin/customer-groups/[id]/route.ts

@@ -0,0 +1,63 @@
+import {
+  updateCustomerGroupsWorkflow,
+  deleteCustomerGroupsWorkflow,
+} from "@medusajs/core-flows"
+import { ModuleRegistrationName } from "@medusajs/modules-sdk"
+import {
+  CustomerGroupUpdatableFields,
+  ICustomerModuleService,
+} from "@medusajs/types"
+import { MedusaRequest, MedusaResponse } from "../../../../types/routing"
+
+export const GET = async (req: MedusaRequest, res: MedusaResponse) => {
+  const customerModuleService = req.scope.resolve<ICustomerModuleService>(
+    ModuleRegistrationName.CUSTOMER
+  )
+
+  const group = await customerModuleService.retrieveCustomerGroup(
+    req.params.id,
+    {
+      select: req.retrieveConfig.select,
+      relations: req.retrieveConfig.relations,
+    }
+  )
+
+  res.status(200).json({ customer_group: group })
+}
+
+export const POST = async (req: MedusaRequest, res: MedusaResponse) => {
+  const updateGroups = updateCustomerGroupsWorkflow(req.scope)
+  const { result, errors } = await updateGroups.run({
+    input: {
+      selector: { id: req.params.id },
+      update: req.validatedBody as CustomerGroupUpdatableFields,
+    },
+    throwOnError: false,
+  })
+
+  if (Array.isArray(errors) && errors[0]) {
+    throw errors[0].error
+  }
+
+  res.status(200).json({ customer_group: result[0] })
+}
+
+export const DELETE = async (req: MedusaRequest, res: MedusaResponse) => {
+  const id = req.params.id
+  const deleteCustomerGroups = deleteCustomerGroupsWorkflow(req.scope)
+
+  const { errors } = await deleteCustomerGroups.run({
+    input: { ids: [id] },
+    throwOnError: false,
+  })
+
+  if (Array.isArray(errors) && errors[0]) {
+    throw errors[0].error
+  }
+
+  res.status(200).json({
+    id,
+    object: "customer_group",
+    deleted: true,
+  })
+}

packages/medusa/src/api-v2/admin/customer-groups/route.ts

@@ -1,5 +1,6 @@
+import { createCustomerGroupsWorkflow } from "@medusajs/core-flows"
 import { ModuleRegistrationName } from "@medusajs/modules-sdk"
-import { ICustomerModuleService } from "@medusajs/types"
+import { CreateCustomerGroupDTO, ICustomerModuleService } from "@medusajs/types"
 import { MedusaRequest, MedusaResponse } from "../../../types/routing"
 
 export const GET = async (req: MedusaRequest, res: MedusaResponse) => {
@@ -17,8 +18,29 @@ export const GET = async (req: MedusaRequest, res: MedusaResponse) => {
 
   res.json({
     count,
-    groups,
+    customer_groups: groups,
     offset,
     limit,
   })
 }
+
+export const POST = async (req: MedusaRequest, res: MedusaResponse) => {
+  const createGroups = createCustomerGroupsWorkflow(req.scope)
+  const customersData = [
+    {
+      ...(req.validatedBody as CreateCustomerGroupDTO),
+      created_by: req.user!.id,
+    },
+  ]
+
+  const { result, errors } = await createGroups.run({
+    input: { customersData },
+    throwOnError: false,
+  })
+
+  if (Array.isArray(errors) && errors[0]) {
+    throw errors[0].error
+  }
+
+  res.status(200).json({ customer_group: result[0] })
+}