How to filter on the contents of an array of objects, with a specified key containing a specified value?

[dnk8n]

Some example of what my PostgREST API returns for the following GET request:

• URL: http://localhost:3000/projects?select=name,locations
• RESPONSE:

[
  {
      "name": "Project 1",
      "locations": [
          {
              "id": 4,
              "name": "Observatory"
          }
      ]
  },
  {
      "name": "Project 2",
      "locations": [
          {
              "id": 10,
              "name": "Monwabisi Park"
          },
          {
              "id": 8,
              "name": "Lotus Park"
          }
      ]
  },
  {
      "name": "Project 3",
      "locations": [
          {
              "id": 20,
              "name": "Hillbrow"
          },
          {
              "id": 4,
              "name": "Observatory"
          },
          {
              "id": 22,
              "name": "eThekwini"
          },
          {
              "id": 21,
              "name": "UMhlathuze"
          }
      ]
  }
]

I want to return only the projects that contain locations id = 4 and can't work this simple filtering out using postgREST fitlering language.

I want to do something along these lines:
http://localhost:3000/projects?select=id,name&locations->id=cs.4

and return just:

[
    {
        "id": 1,
        "name": "Project 1"
    },
    {
        "id": 3,
        "name": "Project 3"
    }
]

[dnk8n]

Maybe better to provide the postgresql query that works:

SELECT id, name
FROM api.projects,
     jsonb_array_elements(locations) elem
WHERE (elem->>'id')::int = 4;

[dnk8n]

Actually, more simple query that works:

SELECT id, name
FROM api.projects
WHERE locations @> '[{"id": 4}]';

[dnk8n]

I found the url I am after:

http://localhost:3000/projects?select=id,name&locations=cs.[{"id": 4}]

with url escaping:

http://localhost:3000/projects?select=id%2Cname&locations=cs.%5B%7B%22id%22%3A%204%7D%5D