<!-- The PR description should answer 2 important questions: -->

### What

Introduce tests for json:api execution. Tests can be defined in any
existing graphql execution folder with the following files:
- `request_jsonapi.json` to define json:api requests. Find a sample
below.
```json
[
  {
    "GET": "/default/Authors"
  },
  {
    "GET": "/default/Authors?fields[author]=author_id,first_name"
  }
]
```
It has support to specify HTTP method, we may introduce `POST` in future
to support mutations, and multiple requests per file.
- `expected_jsonapi.json` contains a 2-d array of responses from
json:api where inner list holds response per request defined in requests
json and outer list corresponds to response list per session variable
set defined in `session_variables.json`.

### How

- Update `common.rs` module in engine tests with json:api test
implementation. Run json:api tests in the same execution code path as
graphql tests utilizing the same metadata.
- Add a sample test.

V3_GIT_ORIGIN_REV_ID: ae74dd7c7c72d764259647a9db93393dacd05306