我有一组随任务发送的标题键。当我在服务器端查看所有包含_的标头时，就会出现问题。如何在标头值中插入_？使用Unicode值？使用UTF-8？如果是这样，在哪里？
request.setValue("4435353", forHTTPHeaderField: "session_id")
request.setValue("08", forHTTPHeaderField: "channel-id")
request.setValue("5afde734-7655-406d-bda3-14ffa968d6ab", forHTTPHeaderField: "itau-client-id")
request.setValue("oO6oO3nW6iG8yV0kL6gU5yY1hE3qV6bH6yF0mK0tG4xX3qU2gD", forHTTPHeaderField: "itau-client-secret")
request.setValue("\(token_latam!)", forHTTPHeaderField: "token_latam")
request.setValue("itoken", forHTTPHeaderField: "application")
request.setValue("2017-12-12T12:30:00", forHTTPHeaderField: "timestamp")
request.setValue("c626ea51-edde-4172-8d16-1c2fd7700c13", forHTTPHeaderField: "itau-chave")
request.setValue("345353454", forHTTPHeaderField: "transaction_id")
request.setValue("\(encoded_operation!)", forHTTPHeaderField: "encoded_operation")
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
服务器端：
{
"itau-chave": "c626ea51-edde-4172-8d16-1c2fd7700c13",
"accept": "*/*",
"timestamp": "2017-12-12T12:30:00",
"itau-client-secret": "oO6oO3nW6iG8yV0kL6gU5yY1hE3qV6bH6yF0mK0tG4xX3qU2gD",
"itau-client-id": "5afde734-7655-406d-bda3-14ffa968d6ab",
"channel-id": "08",
"application": "itoken",
"accept-language": "en-us",
"accept-encoding": "br, gzip, deflate",
"user-agent": "ItauPassEmpresa/1 CFNetwork/975.0.3 Darwin/18.5.0",
"content-type": "application/json"
}