[kemonoparty] restore using default creator posts endpoint

(#7438 #7450 #7462)

- revert c3fb0f53ee
- add '"endpoint": "legacy+"' option
  to use '/posts-legacy' results and with full metadata

docs/configuration.rst

@@ -3112,7 +3112,7 @@ extractor.kemonoparty.endpoint
 Type
     ``string``
 Default
-    ``"legacy"``
+    ``"posts"``
 Description
     API endpoint to use for retrieving creator posts.
 
@@ -3121,6 +3121,13 @@ Description
           `/v1/{service}/user/{creator_id}/posts-legacy <https://kemono.su/documentation/api#operations-default-get_v1__service__user__creator_id__posts_legacy>`__
         | Provides less metadata, but is more reliable at returning all posts.
         | Supports filtering results by ``tag`` query parameter.
+    ``"legacy+"``
+        | Use the results from
+          `/v1/{service}/user/{creator_id}/posts-legacy <https://kemono.su/documentation/api#operations-default-get_v1__service__user__creator_id__posts_legacy>`__
+          to retrieve post IDs
+        | and one request to
+          `/v1/{service}/user/{creator_id}/post/{post_id} <https://kemono.su/documentation/api#operations-Posts-get_v1__service__user__creator_id__post__post_id_>`__
+          to get a full set of metadata for each.
     ``"posts"``
         | Use the results from
           `/v1/{service}/user/{creator_id} <https://kemono.su/documentation/api#operations-Posts-get_v1__service__user__creator_id_>`__