fix: Use User.id.value instead of User.id.toString()

I had implicitly assumed that a value class wrapping a String would
simply return the wrapped String in a toString() call, but this is not
the case.

Fixes #62

app/src/main/kotlin/com/omricat/maplibrarian/chartlist/FirebaseChartsService.kt

@@ -57,7 +57,7 @@ class FirebaseChartsService(
     }
 
     private fun FirebaseFirestore.mapsCollection(user: User) =
-        collection("users").document(user.id.toString()).collection("maps")
+        collection("users").document(user.id.value).collection("maps")
 }
 
 /*

app/src/main/kotlin/com/omricat/maplibrarian/userdetails/UserDetailsViewFactory.kt

@@ -9,6 +9,6 @@ import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 
 internal val UserDetailsViewFactory: ViewFactory<UserDetailsScreen> =
     LayoutRunner.bind(LayoutUserDetailsBinding::inflate) { userDetailsScreen, _ ->
-        userId.text = userDetailsScreen.user.id.id
+        userId.text = userDetailsScreen.user.id.value
         this.btnSignOut.setOnClickListener { userDetailsScreen.onLogOutClicked() }
     }

core/src/main/kotlin/com/omricat/maplibrarian/model/ChartModelMapSerialization.kt

@@ -19,7 +19,7 @@ private object MapModelProperties {
 
 public object ChartModelToMapSerializer : ToMapSerializer<UnsavedChartModel> {
     override operator fun invoke(model: UnsavedChartModel): Map<String, String> =
-        hashMapOf(TITLE to model.title, USER_ID to model.userId.id)
+        hashMapOf(TITLE to model.title, USER_ID to model.userId.value)
 }
 
 public fun UnsavedChartModel.serializedToMap(): Map<String, Any?> = ChartModelToMapSerializer(this)

core/src/main/kotlin/com/omricat/maplibrarian/model/User.kt

@@ -2,7 +2,7 @@ package com.omricat.maplibrarian.model
 
 import kotlinx.serialization.Serializable
 
-@Serializable @JvmInline public value class UserUid(public val id: String)
+@Serializable @JvmInline public value class UserUid(public val value: String)
 
 public interface User {
     public val displayName: String