Upsert credential member

{
  "data": {
    "userId": "string",
    "role": "admin",
    "created": true
  }
}

{
  "data": {
    "userId": "string",
    "role": "admin",
    "created": true
  }
}

{
  "error": {
    "code": "BAD_REQUEST",
    "message": "Invalid request"
  }
}

{
  "error": {
    "code": "UNAUTHORIZED",
    "message": "Authentication required"
  }
}

{
  "error": {
    "code": "FORBIDDEN",
    "message": "Insufficient workspace permissions",
    "details": {
      "code": "INSUFFICIENT_WORKSPACE_ROLE"
    }
  }
}

{
  "error": {
    "code": "NOT_FOUND",
    "message": "Not found"
  }
}

{
  "error": {
    "code": "PAYLOAD_TOO_LARGE",
    "message": "Request body is too large"
  }
}

{
  "error": {
    "code": "UNSUPPORTED_MEDIA_TYPE",
    "message": "Request body must be sent as application/json"
  }
}

{
  "error": {
    "code": "RATE_LIMITED",
    "message": "API rate limit exceeded",
    "details": {
      "retryAfter": "2026-01-01T00:00:30.000Z"
    }
  }
}

{
  "error": {
    "code": "INTERNAL_ERROR",
    "message": "Internal server error"
  }
}

{
  "error": {
    "code": "SERVICE_UNAVAILABLE",
    "message": "Service temporarily unavailable"
  }
}