PATCH action requires all required attributes to be provided

[smt116]

Describe the bug

λ curl -XPATCH -H 'Content-Type: application/vnd.api+json' -d '{"data": {"attributes": {"first_name": "Johny"}}}' -H "Authorization: Basic ..." "http://localhost:4000/api/customers/0194db1f-2294-7459-84e1-45215ffc76ca"  | jq

{
  "errors": [
    {
      "code": "invalid_body",
      "id": "4e9ef680-e3d6-40a5-8bb7-46682a36d0ac",
      "meta": {},
      "status": "400",
      "title": "InvalidBody",
      "source": {
        "pointer": "/data/attributes"
      },
      "detail": "Required properties are missing: [\"email\", \"last_name\"], at [\"data\", \"attributes\"]."
    }
  ],
  "jsonapi": {
    "version": "1.0"
  }
}

The domain exposes patch(:update) JSON API on the resource. The action itself is defined via defaults. It lists attributes that are allow_nil? false.

According to the specification, it should allow this request by updating only included attribute(s) (see https://jsonapi.org/format/#crud-updating-resource-attributes)

To Reproduce
See above.

Expected behavior
The action should allow partial updates via PATCH.

** Runtime

Dependency              Current  Latest   Status
ash                     3.4.62   3.4.62   Up-to-date
ash_json_api            1.4.18   1.4.18   Up-to-date
ash_paper_trail         0.5.0    0.5.0    Up-to-date
ash_phoenix             2.1.17   2.1.17   Up-to-date
ash_postgres            2.5.1    2.5.1    Up-to-date
bandit                  1.6.7    1.6.7    Up-to-date
bcrypt_elixir           3.2.0    3.2.1    Update possible
comeonin                5.5.1    5.5.1    Up-to-date
credo                   1.7.11   1.7.11   Up-to-date
dialyxir                1.4.5    1.4.5    Up-to-date
dns_cluster             0.1.3    0.1.3    Up-to-date
ecto_sql                3.12.1   3.12.1   Up-to-date
esbuild                 0.8.2    0.8.2    Up-to-date
finch                   0.19.0   0.19.0   Up-to-date
floki                   0.37.0   0.37.0   Up-to-date
gettext                 0.26.2   0.26.2   Up-to-date
igniter                 0.5.21   0.5.21   Up-to-date
jason                   1.4.4    1.4.4    Up-to-date
mix_audit               2.1.4    2.1.4    Up-to-date
open_api_spex           3.21.2   3.21.2   Up-to-date
phoenix                 1.7.19   1.7.19   Up-to-date
phoenix_ecto            4.6.3    4.6.3    Up-to-date
phoenix_html            4.2.0    4.2.0    Up-to-date
phoenix_live_dashboard  0.8.6    0.8.6    Up-to-date
phoenix_live_reload     1.5.3    1.5.3    Up-to-date
phoenix_live_view       1.0.4    1.0.4    Up-to-date
postgrex                0.20.0   0.20.0   Up-to-date
sobelow                 0.13.0   0.13.0   Up-to-date
sourceror               1.7.1    1.7.1    Up-to-date
stream_data             1.1.2    1.1.2    Up-to-date
swoosh                  1.17.9   1.17.10  Update possible
tailwind                0.2.4    0.2.4    Up-to-date
telemetry_metrics       1.1.0    1.1.0    Up-to-date
telemetry_poller        1.1.0    1.1.0    Up-to-date

Additional context
Add any other context about the problem here.