feat(region): Add admin region get + list endpoints (#6322)

**What**
Add `GET /admin/regions`
Add `GET /admin/regions/:id`

Blocked by #6320 

Co-authored-by: Adrien de Peretti <25098370+adrien2p@users.noreply.github.com>

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

@@ -0,0 +1,19 @@
+import { remoteQueryObjectFromString } from "@medusajs/utils"
+import { MedusaRequest, MedusaResponse } from "../../../../types/routing"
+import { defaultAdminRegionFields } from "../query-config"
+
+export const GET = async (req: MedusaRequest, res: MedusaResponse) => {
+  const remoteQuery = req.scope.resolve("remoteQuery")
+
+  const variables = { id: req.params.id }
+
+  const queryObject = remoteQueryObjectFromString({
+    entryPoint: "region",
+    variables,
+    fields: defaultAdminRegionFields,
+  })
+
+  const [region] = await remoteQuery(queryObject)
+
+  res.status(200).json({ region })
+}

packages/medusa/src/api-v2/admin/regions/middlewares.ts

@@ -0,0 +1,30 @@
+import { transformQuery } from "../../../api/middlewares"
+import { MiddlewareRoute } from "../../../loaders/helpers/routing/types"
+import * as QueryConfig from "./query-config"
+import {
+  AdminGetRegionsParams,
+  AdminGetRegionsRegionParams,
+} from "./validators"
+
+export const adminRegionRoutesMiddlewares: MiddlewareRoute[] = [
+  {
+    method: ["GET"],
+    matcher: "/admin/regions",
+    middlewares: [
+      transformQuery(
+        AdminGetRegionsParams,
+        QueryConfig.listTransformQueryConfig
+      ),
+    ],
+  },
+  {
+    method: ["GET"],
+    matcher: "/admin/regions/:id",
+    middlewares: [
+      transformQuery(
+        AdminGetRegionsRegionParams,
+        QueryConfig.retrieveTransformQueryConfig
+      ),
+    ],
+  },
+]

packages/medusa/src/api-v2/admin/regions/query-config.ts

@@ -0,0 +1,27 @@
+export const defaultAdminRegionFields = [
+  "id",
+  "name",
+  "currency_code",
+  "created_at",
+  "updated_at",
+  "deleted_at",
+  "metadata",
+  "countries.id",
+  "countries.iso_2",
+  "countries.iso_3",
+  "countries.num_code",
+  "countries.name",
+  "currency.code",
+  "currency.symbol",
+  "currency.symbol_native",
+  "currency.name",
+]
+
+export const retrieveTransformQueryConfig = {
+  isList: false,
+}
+
+export const listTransformQueryConfig = {
+  defaultLimit: 20,
+  isList: true,
+}

packages/medusa/src/api-v2/admin/regions/route.ts

@@ -0,0 +1,20 @@
+import { remoteQueryObjectFromString } from "@medusajs/utils"
+import { MedusaRequest, MedusaResponse } from "../../../types/routing"
+import { defaultAdminRegionFields } from "./query-config"
+
+export const GET = async (req: MedusaRequest, res: MedusaResponse) => {
+  const remoteQuery = req.scope.resolve("remoteQuery")
+
+  const variables = { filters: req.filterableFields }
+
+  const queryObject = remoteQueryObjectFromString({
+    entryPoint: "region",
+    variables,
+    fields: defaultAdminRegionFields,
+  })
+
+  // TODO: Add count, offset, limit
+  const regions = await remoteQuery(queryObject)
+
+  res.json({ regions })
+}

packages/medusa/src/api-v2/admin/regions/validators.ts

@@ -0,0 +1,71 @@
+import { OperatorMap } from "@medusajs/types"
+import { Type } from "class-transformer"
+import { IsOptional, IsString, ValidateNested } from "class-validator"
+import { FindParams, extendedFindParamsMixin } from "../../../types/common"
+import { OperatorMapValidator } from "../../../types/validators/operator-map"
+
+export class AdminGetRegionsRegionParams extends FindParams {}
+
+/**
+ * Parameters used to filter and configure the pagination of the retrieved regions.
+ */
+export class AdminGetRegionsParams extends extendedFindParamsMixin({
+  limit: 50,
+  offset: 0,
+}) {
+  /**
+   * Search parameter for regions.
+   */
+  @IsString({ each: true })
+  @IsOptional()
+  id?: string | string[]
+
+  /**
+   * Filter by currency code
+   */
+  @IsString({ each: true })
+  @IsOptional()
+  code?: string | string[]
+
+  /**
+   * Filter by region name
+   */
+  @IsString({ each: true })
+  @IsOptional()
+  name?: string | string[]
+
+  /**
+   * Date filters to apply on the regions' `created_at` date.
+   */
+  @IsOptional()
+  @ValidateNested()
+  @Type(() => OperatorMapValidator)
+  created_at?: OperatorMap<string>
+
+  /**
+   * Date filters to apply on the regions' `updated_at` date.
+   */
+  @IsOptional()
+  @ValidateNested()
+  @Type(() => OperatorMapValidator)
+  updated_at?: OperatorMap<string>
+
+  /**
+   * Date filters to apply on the regions' `deleted_at` date.
+   */
+  @ValidateNested()
+  @IsOptional()
+  @Type(() => OperatorMapValidator)
+  deleted_at?: OperatorMap<string>
+
+  // Additional filters from BaseFilterable
+  @IsOptional()
+  @ValidateNested({ each: true })
+  @Type(() => AdminGetRegionsParams)
+  $and?: AdminGetRegionsParams[]
+
+  @IsOptional()
+  @ValidateNested({ each: true })
+  @Type(() => AdminGetRegionsParams)
+  $or?: AdminGetRegionsParams[]
+}