Data (Array of Objects) Not Properly Serialized in FormData

[youssefMes]

Description

When using fetch client to send multipart/form-data, arrays of objects included in multipart/form-data requests are not correctly serialized
for example
Example 1 (having more than 1 object):
teamMemberships: [{ userId: 'yh37dt1wfusy79zbax9tqlwi' }, { userId: 'r4vl2q0p4trr0710edspm6qr' },],

await createTeam({
    path: { accountId: 'dummyID' },
    body: {
      name: 'Team 1',
      shortName: 'T1',
      color: 'red',
      teamMemberships: [
        { userId: 'yh37dt1wfusy79zbax9tqlwi' },
        { userId: 'r4vl2q0p4trr0710edspm6qr' },
      ],
    },
  });

Will result in this body (Serialized objects inside the array but the array itself is not)

{
  name: 'Team 1',
  shortName: 'T1',
  color: 'red',
  teamMemberships: [
    '{"userId":"yh37dt1wfusy79zbax9tqlwi"}',
    '{"userId":"r4vl2q0p4trr0710edspm6qr"}'
  ]
}

Example 2 (having only one object in the array): teamMemberships: [{ userId: 'r4vl2q0p4trr0710edspm6qr' }]
Will result in this body (Serialized object but its not an array anymore)

{
  name: 'Team 1',
  shortName: 'T1',
  color: 'red',
  teamMemberships: '{"userId":"yh37dt1wfusy79zbax9tqlwi"}'
}

Expected Behaviour in these cases would be to always receive a serialized array

Reproducible example or configuration

https://stackblitz.com/edit/stackblitz-starters-tn4yru5u?file=app%2Fapi%2F%5BaccountId%5D%2Fteams%2Froute.ts

A demo can be found here, which contains openapi specs file and generated sdk, the output can be seen in the terminal directly after the project setup (logged in the api route located in app/api/[accountId]/teams/route.ts)

OpenAPI specification (optional)

Can be found in stackblitz openapi.json

System information (optional)

No response

[bolt-new-by-stackblitz]

Start a new pull request in StackBlitz Codeflow.

• stackblitz-starters-tn4yru5u (Open reproduction)