DEVDOCS-5710 [add]: Metafields, add metafields batch endpoints

[bc-andreadao]

DEVDOCS-5710

What changed?

• Add endpoints of batch management of metafields

Release notes draft

• The newly-released Metafield endpoints are now available to use. Now, you’ll be able to manage metafields in batches for all types of metafield, including those for product, product variants, and more.

Related PR

• PR 281 for batch metafield endpoint for Locations API
• PR 790 for redirects

[bc-andreadao]

@bc-tayvs Thanks for the review.

Based on your comments (and my testing), I changed the following for the responses:

• 200 responses for POST, PUT, and DELETE methods all have an empty errors array
• 422 responses for the POST, PUT, and DELETE methods all have an empty data array.

I also changed the type for the resource_ids to integer

For your comments on old code/endpoints: I created a new ticket (DEVDOCS-5770), so this PR can focus only on batch endpoints.

Let me know if there's anything else

[bc-tayvs]

@bc-andreadao

422 responses for the POST, PUT, and DELETE methods all have an empty data array.

422 is a partial success, so result could contain data as well as errors. Plz, make data field not empty for this case.
Thanks in advance.

[bc-andreadao]

@bc-tayvs Thanks, just changed the 422 responses so data field isn't empty

[bc-andreadao]

@bc-tayvs I created a new PR 141 to address your comments, if you can review