[hentaicafe] add 'manga_id' metadata field (closes #1036)

This field is only available when using a non-foolslide URL
like '/hc.fyi/9874' or '/hazuki-yuuto-summer-blues/'

gallery_dl/extractor/hentaicafe.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2018-2019 Mike Fährmann
+# Copyright 2018-2020 Mike Fährmann
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 as
@@ -50,17 +50,17 @@ class HentaicafeMangaExtractor(foolslide.FoolslideMangaExtractor):
         # single chapter
         ("https://hentai.cafe/hazuki-yuuto-summer-blues/", {
             "url": "f8e24a07d6fbb7c6a6ec5ad8ad8faf2436f8751b",
-            "keyword": "eb9f98544098c961bd8cf5dbe69e6da51c4fb2f6",
+            "keyword": "5af1c570bb5f533a32b3375f9cdaa17a0152ba67",
         }),
         # multi-chapter
         ("https://hentai.cafe/saitom-saitom-box/", {
             "url": "ca3e8a91531fd6acd863d93ac3afbd8ead06a076",
-            "keyword": "28271062d7b4a2f99a0e1a894f69af8c5581a6bb",
+            "keyword": "3c28517d356cac6acbd9895c9eeefae505304078",
         }),
         # new-style URL
         ("https://hentai.cafe/hc.fyi/2782", {
             "url": "ca3e8a91531fd6acd863d93ac3afbd8ead06a076",
-            "keyword": "28271062d7b4a2f99a0e1a894f69af8c5581a6bb",
+            "keyword": "3c28517d356cac6acbd9895c9eeefae505304078",
         }),
         # foolslide URL
         ("https://hentai.cafe/manga/series/saitom-box/", {
@@ -80,12 +80,14 @@ class HentaicafeMangaExtractor(foolslide.FoolslideMangaExtractor):
             chapters.reverse()
             return chapters
 
-        tags  , pos = text.extract(page, "<p>Tags: ", "</br>")
+        url   , pos = text.extract(page, '<link rel="canonical" href="', '"')
+        tags  , pos = text.extract(page, "<p>Tags: ", "</br>", pos)
         artist, pos = text.extract(page, "\nArtists: ", "</br>", pos)
         manga , pos = text.extract(page, "/manga/read/", "/", pos)
         data = {
-            "tags"  : text.split_html(tags)[::2],
-            "artist": text.split_html(artist),
+            "manga_id": text.parse_int(url.rpartition("/")[2]),
+            "tags"    : text.split_html(tags)[::2],
+            "artist"  : text.split_html(artist),
         }
         HentaicafeChapterExtractor._data(manga).update(data)