The Network Stack

What actually builds the client

PawWalkApi is just an interface — something has to construct the real thing. That's Network.kt: one object, built once, shared by every repository in the app. Three ingredients stack on top of each other:

• OkHttp — the actual HTTP engine underneath Retrofit. It opens connections, sends bytes, receives bytes.
• A converter factory — teaches Retrofit how to turn JSON bytes into Kotlin objects (and back). PawWalk uses kotlinx.serialization's converter, the same annotations (@Serializable, @SerialName) you met in Module 3.
• Retrofit itself — glues a baseUrl, the OkHttp client, and the converter factory together, then .create(PawWalkApi::class.java) produces the real, working implementation of your interface.