Add thumbnail fetch timestamp to the gql manga type (#872)

server/src/main/kotlin/suwayomi/tachidesk/graphql/types/MangaType.kt

@@ -30,6 +30,7 @@ class MangaType(
     val url: String,
     val title: String,
     val thumbnailUrl: String?,
+    val thumbnailUrlLastFetched: Long?,
     val initialized: Boolean,
     val artist: String?,
     val author: String?,
@@ -70,6 +71,7 @@ class MangaType(
         row[MangaTable.url],
         row[MangaTable.title],
         row[MangaTable.thumbnail_url]?.let { MangaList.proxyThumbnailUrl(row[MangaTable.id].value) },
+        row[MangaTable.thumbnailUrlLastFetched],
         row[MangaTable.initialized],
         row[MangaTable.artist],
         row[MangaTable.author],
@@ -90,6 +92,7 @@ class MangaType(
         dataClass.url,
         dataClass.title,
         dataClass.thumbnailUrl,
+        dataClass.thumbnailUrlLastFetched,
         dataClass.initialized,
         dataClass.artist,
         dataClass.author,