android: add notifications foundation with fcm channels and deep links

android/app/src/test/java/ru/daemonlord/messenger/push/PushPayloadParserTest.kt

@@ -0,0 +1,31 @@
+package ru.daemonlord.messenger.push
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class PushPayloadParserTest {
+
+    @Test
+    fun parse_readsChatPayloadFromDataMap() {
+        val payload = PushPayloadParser.parseData(
+            data = mapOf(
+                "chat_id" to "42",
+                "message_id" to "99",
+                "title" to "Alice",
+                "body" to "Hello",
+                "is_mention" to "true",
+            ),
+            notificationTitle = null,
+            notificationBody = null,
+        )
+
+        assertNotNull(payload)
+        assertEquals(42L, payload?.chatId)
+        assertEquals(99L, payload?.messageId)
+        assertEquals("Alice", payload?.title)
+        assertEquals("Hello", payload?.body)
+        assertTrue(payload?.isMention == true)
+    }
+}