Fix conversations (#2556)

* fix conversations

* cleanup ConversationsRemoteMediator

* update conversation timestamps regularly

* improve loadStateListener

* add db migration

* make deleting from conversation db suspending

* reorganize code in ConversationsFragment

* delete NetworkStateViewHolder

* cleanup imports

* add 38.json

* honor fabHide setting in ConversationsFragment

* set page size to 30

app/src/main/java/com/keylesspalace/tusky/network/MastodonApi.kt

@@ -503,8 +503,8 @@ interface MastodonApi {
     @GET("/api/v1/conversations")
     suspend fun getConversations(
         @Query("max_id") maxId: String? = null,
-        @Query("limit") limit: Int
-    ): List<Conversation>
+        @Query("limit") limit: Int? = null
+    ): Response<List<Conversation>>
 
     @DELETE("/api/v1/conversations/{id}")
     suspend fun deleteConversation(