[bluesky] add 'search' extractor (#4438)

Both https://bsky.app/search?q=QUERY and https://bsky.app/search/QUERY
are recognized as search URLs, where QUERY gets forwarded unmodified as
'q' parameter for app.bsky.feed.searchPosts .

User searches are not supported yet.

docs/supportedsites.md

@@ -124,7 +124,7 @@ Consider all listed sites to potentially be NSFW.
 <tr>
     <td>Bluesky</td>
     <td>https://bsky.app/</td>
-    <td>Feeds, Followed Users, Likes, Lists, Media Files, Posts, Replies, User Profiles</td>
+    <td>Avatars, Backgrounds, Feeds, Followed Users, Likes, Lists, Media Files, Posts, Replies, Search Results, User Profiles</td>
     <td>Supported</td>
 </tr>
 <tr>

gallery_dl/extractor/bluesky.py

@@ -43,7 +43,8 @@ def _init(self):
 
     def items(self):
         for post in self.posts():
-            post = post["post"]
+            if "post" in post:
+                post = post["post"]
             post.update(post["record"])
             del post["record"]
 
@@ -265,6 +266,15 @@ def posts(self):
         return self._make_post(self.user, "banner")
 
 
+class BlueskySearchExtractor(BlueskyExtractor):
+    subcategory = "search"
+    pattern = BASE_PATTERN + r"/search(?:/|\?q=)(.+)"
+    example = "https://bsky.app/search?q=QUERY"
+
+    def posts(self):
+        return self.api.search_posts(self.user)
+
+
 class BlueskyAPI():
     """Interface for the Bluesky API
 
@@ -360,6 +370,14 @@ def resolve_handle(self, handle):
         params = {"handle": handle}
         return self._call(endpoint, params)["did"]
 
+    def search_posts(self, query):
+        endpoint = "app.bsky.feed.searchPosts"
+        params = {
+            "q"    : query,
+            "limit": "100",
+        }
+        return self._pagination(endpoint, params, "posts")
+
     def _did_from_actor(self, actor):
         if actor.startswith("did:"):
             did = actor