The order endpoint is used to submit a UniswapX intent. If the routing field in the response to a quote is any of DUTCH_V2, DUTCH_V3, or PRIORITYQUOTE this endpoint is used to submit your order to the UniswapX protocol to be filled by the filler network. These orders are gasless because the filler will pay the gas to complete the transaction.
The order will be validated and, if valid, will be submitted to the filler network. The network will try to fill the order at the quoted startAmount. If the order is not filled at the startAmount by the deadline, the amount will start decaying until the endAmount is reached. The order will remain open until it is either filled, canceled, or has expired by remaining unfilled beyond the decayEndTime.
For simplicity, the order request is identical to the quote response except for the addition of the signed permit.