Change record status: 
Project: 
Introduced in branch: 
9.3.x
Introduced in version: 
9.3.0
Description: 

In the jsonapi module all references to entities are done by UUID's. This is consistent but this means in the previous release it was impossible to filter by its (more readable) target_id.

This change exposed the target_id in the meta information for a Resource. Making it more readable, easier to code against and filterable.

Example where node_type is now actually readable.

{
  "jsonapi": {...},
  "data": [
    {
      "type": "node--article",
      "id": "0fe30767-31c6-4c97-9a19-83402eda782e",
      "links": {...},
      "attributes": {...},
      "relationships": {
        "node_type": {
          "data": {
            "type": "node_type--node_type",
            "id": "0c2b2d5b-83b1-4235-b5b8-9b43a168230b",
            "meta": {
              "drupal_internal__target_id": "article"
            }
          }
        },
        "field_tags": {
          "data": [
            {
              "type": "taxonomy_term--tags",
              "id": "e9436484-81cf-481a-8e03-64450e6bd20c",
              "meta": {
                "drupal_internal__target_id": 2
              }
            },
            {
              "type": "taxonomy_term--tags",
              "id": "86de8f96-ee71-4ca1-9ac1-e4be5a7ade0f",
              "meta": {
                "drupal_internal__target_id": 4
              }
            },
            {
              "type": "taxonomy_term--tags",
              "id": "a22aa858-f8b6-463c-8e64-2867e8da6b51",
              "meta": {
                "drupal_internal__target_id": 6
              }
            }
          ],
          "links": {...}
        },
        "links": {...}
      }
    }
  ],
  "links": {...}
}

This also makes is possible to filter on target_id instead of UUID's.

Filter before:
/jsonapi/node/article?filter[field_tags.id]=e9436484-81cf-481a-8e03-64450e6bd20c

Now allowed:
/jsonapi/node/article?filter[field_tags.meta.drupal_internal__target_id]=2

Impacts: 
Module developers
Themers
Updates Done (doc team, etc.)
Online documentation: 
Generic online documentation done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other: 
Other updates done
Details: 

Documentation update

Progress: 
Documentation updated: https://www.drupal.org/docs/core-modules-and-themes/core-modules/jsonapi-module/filtering#comment-14134887