Fix status diffing and improve timeline performance (#2386)

* fix status & account diffing

* introduce TimelineAccount

* use TimelineAccount where possible

* improve tests

* improve ConversationEntity equals/hashcode

* fix mistake in ConversationEntity

* improve StatusViewData comparison

* improve tests

* fix typo in comment

app/src/main/java/com/keylesspalace/tusky/entity/TimelineAccount.kt

@@ -0,0 +1,39 @@
+/* Copyright 2017 Andrew Dawson
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
+package com.keylesspalace.tusky.entity
+
+import com.google.gson.annotations.SerializedName
+
+/**
+ * Same as [Account], but only with the attributes required in timelines.
+ * Prefer this class over [Account] because it uses way less memory & deserializes faster from json.
+ */
+data class TimelineAccount(
+    val id: String,
+    @SerializedName("username") val localUsername: String,
+    @SerializedName("acct") val username: String,
+    @SerializedName("display_name") val displayName: String?, // should never be null per Api definition, but some servers break the contract
+    val url: String,
+    val avatar: String,
+    val bot: Boolean = false,
+    val emojis: List<Emoji>? = emptyList(), // nullable for backward compatibility
+) {
+
+    val name: String
+        get() = if (displayName.isNullOrEmpty()) {
+            localUsername
+        } else displayName
+}