Add collapsed state to header

app/src/googleplay/java/org/tasks/wear/WearService.kt

@@ -87,7 +87,7 @@ class WearService(
                                     .setId(item.value)
                                     .setType(ListItemType.Header)
                                     .setTitle(headerFormatter.headerString(item.value, style = DateStyle.MEDIUM))
-                                    .setCollapsed(collapsed.contains(item.value))
+                                    .setCollapsed(item.collapsed)
                                     .build()
 
                             is UiItem.Task -> {

kmp/src/commonMain/kotlin/org/tasks/tasklist/SectionedDataSource.kt

@@ -51,7 +51,7 @@ class SectionedDataSource(
 
     override fun get(index: Int) =
         sections[index]
-            ?.let { UiItem.Header(it.value) }
+            ?.let { UiItem.Header(it.value, it.collapsed) }
             ?: UiItem.Task(getItem(index))
 
     override fun isEmpty() = size == 0

kmp/src/commonMain/kotlin/org/tasks/tasklist/UiItem.kt

@@ -3,6 +3,16 @@ package org.tasks.tasklist
 import org.tasks.data.TaskContainer
 
 sealed class UiItem {
-    data class Header(val value: Long): UiItem()
-    data class Task(val task: TaskContainer): UiItem()
+    data class Header(
+        val value: Long,
+        val collapsed: Boolean,
+    ) : UiItem()
+
+    data class Task(val task: TaskContainer) : UiItem()
+
+    val key: String
+        get() = when (this) {
+            is Header -> "header_$value"
+            is Task -> task.id.toString()
+        }
 }