Add custom Thumbnail Url. Support backup & restore (#1059)

* Add custom thumbnail url. Support backup & restore

- add custom thumbnail url in edit info/custom
- include it in backup n restore

* increase chop char

* edit chop char again to match screenshoot

* tweak truncating middle part

* apply edited cover to history, updates , others

* simplify placeholder logic

---------

Co-authored-by: jobobby04 <jobobby04@users.noreply.github.com>

source-api/src/commonMain/kotlin/eu/kanade/tachiyomi/source/model/SManga.kt

@@ -33,6 +33,7 @@ interface SManga : Serializable {
     val originalTitle: String
     val originalAuthor: String?
     val originalArtist: String?
+    val originalThumbnailUrl: String?
     val originalDescription: String?
     val originalGenre: String?
     val originalStatus: Int
@@ -44,11 +45,11 @@ interface SManga : Serializable {
         it.title = originalTitle
         it.artist = originalArtist
         it.author = originalAuthor
+        it.thumbnail_url = originalThumbnailUrl
         it.description = originalDescription
         it.genre = originalGenre
         it.status = originalStatus
         // SY <--
-        it.thumbnail_url = thumbnail_url
         it.update_strategy = update_strategy
         it.initialized = initialized
     }
@@ -103,7 +104,7 @@ fun SManga.copy(
     description: String? = this.originalDescription,
     genre: String? = this.originalGenre,
     status: Int = this.status,
-    thumbnail_url: String? = this.thumbnail_url,
+    thumbnail_url: String? = this.originalThumbnailUrl,
     initialized: Boolean = this.initialized,
 ) = SManga.create().also {
     it.url = url

source-api/src/commonMain/kotlin/eu/kanade/tachiyomi/source/model/SMangaImpl.kt

@@ -31,6 +31,8 @@ class SMangaImpl : SManga {
         get() = author
     override val originalArtist: String?
         get() = artist
+    override val originalThumbnailUrl: String?
+        get() = thumbnail_url
     override val originalDescription: String?
         get() = description
     override val originalGenre: String?