Function adapter

tests/unit/api.test.js:84–95

(config)

          await axios[method]('/test', {
            adapter(config) {
              seenData = config.data;

              return Promise.resolve({
                data: null,
                status: 200,
                statusText: 'OK',
                headers: {},
                config,
                request: {},
              });
            },
          });

          assert.strictEqual(seenData, undefined);