feat(medusa): handle product categories in import/export strategies (#3842)

**What**
- add ProductCategories to import and export strategies
- refactor ProductCategoriesService methods to use "retrieve_" pattern

---

RESOLVES CORE-1275

integration-tests/api/__tests__/batch-jobs/product/ff-product-category.js

@@ -0,0 +1,165 @@
+const fs = require("fs")
+const path = require("path")
+
+const { useApi } = require("../../../../helpers/use-api")
+const { useDb } = require("../../../../helpers/use-db")
+
+const adminSeeder = require("../../../helpers/admin-seeder")
+const userSeeder = require("../../../helpers/user-seeder")
+const { simpleProductCategoryFactory } = require("../../../factories")
+const batchJobSeeder = require("../../../helpers/batch-job-seeder")
+const {
+  simpleProductCollectionFactory,
+} = require("../../../factories/simple-product-collection-factory")
+
+const startServerWithEnvironment =
+  require("../../../../helpers/start-server-with-environment").default
+
+jest.setTimeout(30000)
+
+function getImportFile() {
+  return path.resolve(
+    "__tests__",
+    "batch-jobs",
+    "product",
+    "product-import-pc.csv"
+  )
+}
+
+function copyTemplateFile() {
+  const csvTemplate = path.resolve(
+    "__tests__",
+    "batch-jobs",
+    "product",
+    "product-import-pc-template.csv"
+  )
+  const destination = getImportFile()
+  fs.copyFileSync(csvTemplate, destination)
+}
+
+const adminReqConfig = {
+  headers: {
+    Authorization: "Bearer test_token",
+  },
+}
+
+function cleanTempData() {
+  // cleanup tmp ops files
+  const opsFiles = path.resolve("__tests__", "batch-jobs", "product", "imports")
+
+  fs.rmSync(opsFiles, { recursive: true, force: true })
+}
+
+describe("Product import - Product Category", () => {
+  let cat
+  let dbConnection
+  let medusaProcess
+
+  const collectionHandle1 = "test-collection1"
+
+  beforeAll(async () => {
+    const cwd = path.resolve(path.join(__dirname, "..", "..", ".."))
+
+    cleanTempData()
+
+    const [process, connection] = await startServerWithEnvironment({
+      cwd,
+      env: { MEDUSA_FF_PRODUCT_CATEGORIES: true },
+      uploadDir: __dirname,
+    })
+    dbConnection = connection
+    medusaProcess = process
+  })
+
+  afterAll(async () => {
+    const db = useDb()
+    await db.shutdown()
+
+    cleanTempData()
+    medusaProcess.kill()
+  })
+
+  beforeEach(async () => {
+    try {
+      await batchJobSeeder(dbConnection)
+      await adminSeeder(dbConnection)
+      await userSeeder(dbConnection)
+
+      await simpleProductCategoryFactory(dbConnection, {
+        name: "category",
+        handle: "import-category-1",
+      })
+
+      await simpleProductCollectionFactory(dbConnection, {
+        handle: collectionHandle1,
+      })
+    } catch (e) {
+      console.log(e)
+      throw e
+    }
+  })
+
+  afterEach(async () => {
+    const db = useDb()
+    return await db.teardown()
+  })
+
+  it("Import products with an existing product category", async () => {
+    jest.setTimeout(1000000)
+    const api = useApi()
+
+    copyTemplateFile()
+
+    const response = await api.post(
+      "/admin/batch-jobs",
+      {
+        type: "product-import",
+        context: {
+          fileKey: "product-import-pc.csv",
+        },
+      },
+      adminReqConfig
+    )
+
+    const batchJobId = response.data.batch_job.id
+
+    let batchJob
+    let shouldContinuePulling = true
+    while (shouldContinuePulling) {
+      const res = await api.get(
+        `/admin/batch-jobs/${batchJobId}`,
+        adminReqConfig
+      )
+
+      await new Promise((resolve, _) => {
+        setTimeout(resolve, 1000)
+      })
+
+      batchJob = res.data.batch_job
+
+      shouldContinuePulling = !(
+        batchJob.status === "completed" || batchJob.status === "failed"
+      )
+    }
+
+    expect(batchJob.status).toBe("completed")
+
+    const productsResponse = await api.get(
+      "/admin/products?expand=categories",
+      adminReqConfig
+    )
+
+    expect(productsResponse.data.count).toBe(1)
+    expect(productsResponse.data.products).toEqual([
+      expect.objectContaining({
+        title: "Test product",
+        handle: "test-product-product-1",
+        categories: [
+          expect.objectContaining({
+            handle: "import-category-1",
+          }),
+        ],
+      }),
+    ])
+  })
+})

integration-tests/api/__tests__/batch-jobs/product/product-import-pc-template.csv

@@ -0,0 +1,2 @@
+Product Id,Product Handle,Product Title,Product Subtitle,Product Description,Product Status,Product Thumbnail,Product Weight,Product Length,Product Width,Product Height,Product HS Code,Product Origin Country,Product MID Code,Product Material,Product Collection Title,Product Collection Handle,Product Type,Product Tags,Product Discountable,Product External Id,Variant Id,Variant Title,Variant SKU,Variant Barcode,Variant Inventory Quantity,Variant Allow Backorder,Variant Manage Inventory,Variant Weight,Variant Length,Variant Width,Variant Height,Variant HS Code,Variant Origin Country,Variant MID Code,Variant Material,Price ImportLand [EUR],Price USD,Price denmark [DKK],Price Denmark [DKK],Option 1 Name,Option 1 Value,Option 2 Name,Option 2 Value,Image 1 Url,Product Category 1 Handle
+,test-product-product-1,Test product,,"Hopper Stripes Bedding, available as duvet cover, pillow sham and sheet.\n100% organic cotton, soft and crisp to the touch. Made in Portugal.",draft,,,,,,,,,,Test collection 1,test-collection1,test-type-1,123_1,TRUE,,,Test variant,test-sku-1,test-barcode-1,10,FALSE,TRUE,,,,,,,,,1.00,1.10,1.30,,test-option-1,option 1 value red,test-option-2,option 2 value 1,test-image.png,import-category-1