[docs] Fix inconsistency about which sites have optional authentication (#359)

* [docs] Fix inconsistency about which sites have optional authentication

* update authentication docs

README.rst

@@ -168,10 +168,11 @@ Username & Password
 -------------------
 
 Some extractors require you to provide valid login-credentials in the form of
-a username & password pair.
-This is necessary for ``pixiv``, ``nijie`` and ``seiga``
-and optional (but strongly recommended) for ``exhentai``,  ``luscious``,
-``sankaku``, ``idolcomplex``, ``tsumino`` and ``wallhaven``.
+a username & password pair. This is necessary for
+``pixiv``, ``nijie``, and ``seiga``
+and optional (but strongly recommended) for
+``danbooru``, ``exhentai``, ``idolcomplex``, ``instagram``,
+``luscious``, ``sankaku``, ``tsumino``, and ``twitter``.
 
 You can set the necessary information in your configuration file
 (cf. gallery-dl.conf_)

docs/configuration.rst

@@ -164,10 +164,11 @@ Default     ``null``
 Description The username and password to use when attempting to log in to
             another site.
 
-            Specifying username and password is
-            required for the ``pixiv``, ``nijie`` and ``seiga`` modules and
-            optional (but strongly recommended) for ``danbooru``, ``exhentai``,
-            ``sankaku`` and ``idolcomplex``.
+            Specifying username and password is required for the
+            ``pixiv``, ``nijie``, and ``seiga``
+            modules and optional (but strongly recommended) for
+            ``danbooru``, ``exhentai``, ``idolcomplex``, ``instagram``,
+            ``luscious``, ``sankaku``, ``tsumino``, and ``twitter``.
 
             These values can also be set via the ``-u/--username`` and
             ``-p/--password`` command-line options or by using a |.netrc|_ file.

docs/supportedsites.rst

@@ -108,7 +108,7 @@ Tsumino              https://www.tsumino.com/            Galleries, Search Resul
 Tumblr               https://www.tumblr.com/             Images from Users, Likes, Posts, Tag-Searches      Optional (OAuth)
 Twitter              https://twitter.com/                Media Timelines, Timelines, Tweets                 Optional
 VSCO                 https://vsco.co/                    Images from Users, Collections, individual Images
-Wallhaven            https://wallhaven.cc/               individual Images, Search Results
+Wallhaven            https://wallhaven.cc/               individual Images, Search Results                  |wallhaven-A|
 Warosu               https://warosu.org/                 Threads
 Weibo                https://www.weibo.com/              Images from Users, Images from Statuses
 WikiArt.org          https://www.wikiart.org/            Artists, Artworks
@@ -139,4 +139,5 @@ Turboimagehost       https://www.turboimagehost.com/     individual Images
 .. |pixnet-C| replace:: Images from Users, Folders, individual Images, Sets
 .. |pornreactor-C| replace:: Images from Users, Posts, Search Results, Tag-Searches
 .. |smugmug-C| replace:: Albums, individual Images, Images from Users and Folders
+.. |wallhaven-A| replace:: Optional (`API Key <configuration.rst#extractorwallhavenapi-key>`__)
 .. |yuki-S| replace:: yuki.la 4chan archive

scripts/supportedsites.py

@@ -123,6 +123,8 @@ AUTH_MAP = {
     "tsumino"    : "Optional",
     "tumblr"     : "Optional (OAuth)",
     "twitter"    : "Optional",
+    "wallhaven"  : ("Optional (`API Key "
+                    "<configuration.rst#extractorwallhavenapi-key>`__)"),
 }
 
 IGNORE_LIST = (