curl --request POST \
  --url https://grid.squads.xyz/api/grid/v1/accounts/{address}/proposals \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'x-grid-environment: <x-grid-environment>' \
  --data '
{
  "signer": "<string>",
  "transaction": "<string>",
  "type": "custom",
  "fee_config": "<unknown>"
}
'

{
  "data": {
    "proposalAddress": "<string>",
    "signer": "<string>",
    "transactions": [
      "<string>"
    ]
  },
  "metadata": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z"
  }
}