Makes the alamofire can encode protobuf easily

Alamofire+Protobuf.swift

import Foundation
import Alamofire

open class ProtobufParameterEncoder: ParameterEncoder {
    
    /// Returns an encoder with default parameters.
    public static var `default`: ProtobufParameterEncoder { ProtobufParameterEncoder() }

    public init() {}

    open func encode<Parameters>(_ parameters: Parameters?,
                                            into request: URLRequest) throws -> URLRequest {
        guard let parameters = parameters else { return request }

        var request = request

        request.httpBody = parameters as? Data
        if request.headers["Content-Type"] == nil {
            request.headers.update(.contentType("application/x-protobuf"))
        }

        return request
    }
}

extension ParameterEncoder where Self == ProtobufParameterEncoder {
    /// Provides a default `ProtobufParameterEncoder` instance.
    public static var protobuf: ProtobufParameterEncoder { ProtobufParameterEncoder() }
}

Usage

let response = await AF.request(
    ...
    parameters: try! protobufModel.serializedData(),
    encoder: .protobuf
).serializingData().response