Use SYNC1 as DAVx5 etag

app/src/main/java/org/tasks/data/OpenTaskDao.kt

@@ -62,18 +62,18 @@ class OpenTaskDao @Inject constructor(
         calendars
     }
 
-    suspend fun getEtags(listId: Long): List<Triple<String, String, String>> = withContext(Dispatchers.IO) {
-        val items = ArrayList<Triple<String, String, String>>()
+    suspend fun getEtags(listId: Long): List<Triple<String, String?, String>> = withContext(Dispatchers.IO) {
+        val items = ArrayList<Triple<String, String?, String>>()
         cr.query(
                 tasks,
-                arrayOf(Tasks._SYNC_ID, Tasks.SYNC_VERSION, "version"),
+                arrayOf(Tasks._SYNC_ID, Tasks.SYNC1, "version"),
                 "${Tasks.LIST_ID} = $listId",
                 null,
                 null)?.use {
             while (it.moveToNext()) {
                 items.add(Triple(
                         it.getString(Tasks._SYNC_ID)!!,
-                        it.getLong(Tasks.SYNC_VERSION).toString(),
+                        it.getString(Tasks.SYNC1),
                         it.getLong("version").toString()))
             }
         }

app/src/main/java/org/tasks/opentasks/OpenTasksSynchronizer.kt

@@ -159,9 +159,9 @@ class OpenTasksSynchronizer @Inject constructor(
         }
 
         val etags = openTaskDao.getEtags(listId)
-        etags.forEach { (syncId, syncVersion, version) ->
+        etags.forEach { (syncId, sync1, version) ->
             val caldavTask = caldavDao.getTask(calendar.uuid!!, syncId)
-            val etag = if (isEteSync) version else syncVersion
+            val etag = if (isEteSync) version else sync1
             if (caldavTask?.etag == null || caldavTask.etag != etag) {
                 applyChanges(calendar, listId, syncId, etag, caldavTask)
             }
@@ -265,7 +265,7 @@ class OpenTasksSynchronizer @Inject constructor(
             calendar: CaldavCalendar,
             listId: Long,
             syncId: String,
-            etag: String,
+            etag: String?,
             existing: CaldavTask?) {
         cr.query(
                 Tasks.getContentUri(openTaskDao.authority),