Create custom saver for Set<AboutInputField>

There's a crash caused by rememberSaveable { mutableStateOf(AboutInputField.all) }
The default saver doesn't support non-primitive types.

Author: AdamGrzybkowski

demo-app/src/main/java/com/gravatar/demoapp/ui/AvatarUpdateTab.kt

@@ -89,7 +89,9 @@ fun AvatarUpdateTab(modifier: Modifier = Modifier) {
     val coroutineScope = rememberCoroutineScope()
     var cacheBuster: String? by remember { mutableStateOf(null) }
     val scrollState: ScrollState = rememberScrollState()
-    var aboutFields: Set<AboutInputField> by rememberSaveable { mutableStateOf(AboutInputField.all) }
+    var aboutFields: Set<AboutInputField> by rememberSaveable(stateSaver = AboutInputFieldSetSaver) {
+        mutableStateOf(AboutInputField.all)
+    }
     var pickerContentLayout: AvatarPickerContentLayout by rememberSaveable(
         stateSaver = AvatarPickerContentLayoutSaver,
     ) {
@@ -502,6 +504,11 @@ private fun InitialPageDropdown(
     }
 }
 
+private val AboutInputFieldSetSaver = Saver<Set<AboutInputField>, List<AboutInputField>>(
+    save = { it.toList() },
+    restore = { it.toSet() },
+)
+
 private val AvatarPickerContentLayoutSaver: Saver<AvatarPickerContentLayout, String> = run {
     val horizontalKey = "horizontal"
     val verticalKey = "vertical"