[discord] add support (mikf#6836)

* first commit

* add --

* skip video embeds

* fix typo

* removed ambiguity

* add category support

* code tweaks

* more reliable embed extraction

* handle 403 errors (testing done)

* added "parent_id" keyword

* added "parent", "parent_type" keywords

the extractor should be now ready to merge!

* removed unnecessary dict unpacking

* added empty text messages extraction

* added "channel_topic"

* even more metadata extraction

can now extract all embeds images & text, as well as server banners. also code is much better.

* added user avatar and banner

* better pagination

* fix regression

* minor tweaks

* Made requested changes

docs/configuration.rst

@@ -2210,6 +2210,39 @@ Description
     | Leave ``SIZE`` empty to download the regular, small avatar format.
 
 
+extractor.discord.embeds
+------------------------
+Type
+    ``list`` of ``strings``
+Default
+    ``["image", "gifv", "video"]``
+Description
+    Selects which embed types to download from.
+
+    Supported embed types are
+    ``image``, ``gifv``, ``video``, ``rich``, ``article``, ``link``.
+
+
+extractor.discord.threads
+-------------------------
+Type
+    ``bool``
+Default
+    ``true``
+Description
+    Extract threads from Discord text channels.
+
+
+extractor.discord.token
+-----------------------
+Type
+    ``string``
+Description
+    Discord Bot Token for API requests.
+
+    You can follow `this guide <https://github.com/Tyrrrz/DiscordChatExporter/blob/master/.docs/Token-and-IDs.md#how-to-get-a-user-token>`__ to get a token.
+
+
 extractor.[E621].metadata
 -------------------------
 Type

docs/supportedsites.md

@@ -205,6 +205,12 @@ Consider all listed sites to potentially be NSFW.
     <td>Avatars, Backgrounds, Collections, Deviations, Favorites, Folders, Followed Users, Galleries, Gallery Searches, Journals, Scraps, Search Results, Sta.sh, Status Updates, Tag Searches, User Profiles, Watches</td>
     <td><a href="https://github.com/mikf/gallery-dl#oauth">OAuth</a></td>
 </tr>
+<tr>
+    <td>Discord</td>
+    <td>https://discord.com/</td>
+    <td>Channels, DMs, Servers</td>
+    <td></td>
+</tr>
 <tr>
     <td>Dynasty Reader</td>
     <td>https://dynasty-scans.com/</td>

gallery_dl/extractor/__init__.py

@@ -44,6 +44,7 @@
     "danbooru",
     "desktopography",
     "deviantart",
+    "discord",
     "dynastyscans",
     "e621",
     "erome",