我试图通过添加.addHeader（）到OkHttpClient.Builder（）中来为每个请求添加自定义头，但在构建时出现以下错误：
MicroApiClient.kt:（16，14）：未解析参考：addHeader
如何使用下面的代码正确地将自定义头添加到每个请求？

package com.app.name.data
    
    import com.app.name.BuildConfig
    import com.app.name.data.source.remote.APPService
    import okhttp3.OkHttpClient
    import okhttp3.logging.HttpLoggingInterceptor
    import retrofit2.Retrofit
    import retrofit2.converter.gson.GsonConverterFactory
    import retrofit2.converter.scalars.ScalarsConverterFactory
    
    object MicroApiClient {
        private val loggingInterceptor = HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BODY)
        private val okHttpClient = OkHttpClient.Builder()
                .addInterceptor(loggingInterceptor)
                // Attempting to add headers to every request
                .addHeader("x-api-key", BuildConfig.AWS_MICROSERVICES_API_KEY)
                .build()
        val instance: APPService by lazy {
            val retrofit = Retrofit.Builder()
                    .baseUrl(BuildConfig.AWS_MICROSERVICES_HOST)
                    .addConverterFactory(GsonConverterFactory.create())
                    .addConverterFactory(ScalarsConverterFactory.create())
                    .client(okHttpClient)
                    .build()
    
            retrofit.create(APPService::class.java)
        }
    }