Подпись запроса в ktor

KtorSignerFeature.kt

package com.example.data.network.features

import io.ktor.client.HttpClient
import io.ktor.client.features.HttpClientFeature
import io.ktor.client.request.HttpRequestBuilder
import io.ktor.client.request.HttpRequestPipeline
import io.ktor.client.request.header
import io.ktor.content.TextContent
import io.ktor.http.clone
import io.ktor.util.AttributeKey
import com.example.domain.extensions.md5

/**
 * Формирует подпись запроса и добавляет её в соответствующий заголовок
 */
class MyCustomSigner(private val apiUrl: String, private val apiKey: String) {

    class Config {
        var apiUrl = ""
        var apiKey = ""
    }

    companion object Feature : HttpClientFeature<Config, MyCustomSigner> {

        override val key = AttributeKey<MyCustomSigner>("MyCustomSigner")

        private fun HttpRequestBuilder.buildSign(feature: MyCustomSigner, body: TextContent?): String {
            val parts = mutableListOf<String>()
            parts += method.value
            parts += url.clone().buildString().substringAfter(feature.apiUrl)
            parts += headers[MyCustomHeaders.ApiUser] ?: ""
            parts += headers[MyCustomHeaders.ApiPassword] ?: ""
            parts += headers[MyCustomHeaders.ClientLogin] ?: ""
            parts += headers[MyCustomHeaders.ClientPasswordHash] ?: ""
            parts += body?.text ?: ""
            parts += headers[MyCustomHeaders.ClientUid] ?: ""
            parts += feature.apiKey
            return parts.joinToString(":").md5
        }

        override fun prepare(block: Config.() -> Unit): MyCustomSigner {
            val config = Config().apply(block)
            return MyCustomSigner(config.apiUrl, config.apiKey)
        }

        override fun install(feature: MyCustomSigner, scope: HttpClient) {
            scope.requestPipeline.intercept(HttpRequestPipeline.Transform) { payload ->
                val hash = context.buildSign(feature, payload as? TextContent)
                context.header(MyCustomHeaders.Hash, hash)
                proceed()
            }
        }

    }
}