How to setup phone auth? [No proper documentation found]

[Custard-app]

I am trying to setup the phone auth for our kmm app but I was unable to find the proper documentation regarding this. I tried to read the codebase and implement the things accordingly but I was unable to do so. Please check below implementation.

         val callback = object :PhoneVerificationProvider{}
          // sms verification
          val cred = PhoneAuthProvider().verifyPhoneNumber(
              phoneNumber,
              callback
          )
          val result =  Firebase.auth.signInWithCredential(cred)
          Napier.d { "$result" }

In the above implementation the interface is not implemented correctly and I am getting the error while compiling which is mentioned below.

Object is not abstract and does not implement abstract member public abstract val activity: Activity defined in dev.gitlive.firebase.auth.PhoneVerificationProvider