Implement `ProductImportStrategy`

[fPolic]

• add ProductImportStrategy class for processing products batch import which implements the common batch job strategy interface

• depends on: https://github.com/medusajs/medusa/issues/1264

DoD

• [ ] When dry_run: true ProductImportStrategy should first move BatchJob to an awaiting_confirmation state before importing data.

  // pre-confirmation.json

  [
    { operation: "create", type: "product", data: { .... },
    { operation: "create", type: "product-variant", data: { ... }
  ]

  // ON CONFIRM

  await Promise.all(preconfirmops.map((op) => {
    switch(op.operation) 
      case "create":
        productService.create(op.data)
        break
      case "update":
        productVariantService.update(op.existing_id, op.data)
  }))

• [ ] Should create a summary of the data to be imported e.g. create_count: 32, update_count: 13, error_count: 2 which should be kept in the BatchJob result until completion.
• [ ] Should report progress to the BatchJobService
• [ ] The default import format should support the same columns as the export format

View more from the discussion here

The required fields for a new product are:

• handle, title
• Other fields that have defaults if not provided:
  • Status - draft
  • Product Option 1 - Default Option
  • Profile - Default Profile
  • Discountable - true

The required fields for a new product variant are:

• If product has product option then Variant Option Value must be defined
• Other fields that have defaults if not provided:
  • Title - concat of option values
  • Allow Backorder - false
  • Manage Inventory - true
  • Variant Option Value 1 (if not defined on product) - Default Variant

Fixes CORE-413

[srindom]

DoD

• [ ] When dry_run: true ProductImportStrategy should first move BatchJob to an awaiting_confirmation state before importing data.

  // pre-confirmation.json

  [
    { operation: "create", type: "product", data: { .... },
    { operation: "create", type: "product-variant", data: { ... }
  ]

  // ON CONFIRM

  await Promise.all(preconfirmops.map((op) => {
    switch(op.operation) 
      case "create":
        productService.create(op.data)
        break
      case "update":
        productVariantService.update(op.existing_id, op.data)
  }))

• [ ] Should create a summary of the data to be imported e.g. create_count: 32, update_count: 13, error_count: 2 which should be kept in the BatchJob result until completion.
• [ ] Should report progress to the BatchJobService
• [ ] The default import format should support the same columns as the export format

View more from the discussion here

The required fields for a new product are:

• handle, title
• Other fields that have defaults if not provided:
  • Status - draft
  • Product Option 1 - Default Option
  • Profile - Default Profile
  • Discountable - true

The required fields for a new product variant are:

• If product has product option then Variant Option Value must be defined
• Other fields that have defaults if not provided:
  • Title - concat of option values
  • Allow Backorder - false
  • Manage Inventory - true
  • Variant Option Value 1 (if not defined on product) - Default Variant