server/search: allow searching by source URL content

client/html/help_search_posts.tpl

@@ -38,6 +38,10 @@
             <td><code>fav</code></td>
             <td>favorited by given user (accepts wildcards)</td>
         </tr>
+        <tr>
+            <td><code>source</code></td>
+            <td>having given source URL (accepts wildcards)</td>
+        </tr>
         <tr>
             <td><code>tag-count</code></td>
             <td>having given number of tags</td>

server/szurubooru/search/configs/post_search_config.py

@@ -230,6 +230,11 @@ class PostSearchConfig(BaseSearchConfig):
                 _create_score_filter(-1)
             ),
 
+            (
+                ['source'],
+                search_util.create_str_filter(model.Post.source)
+            ),
+
             (
                 ['tag-count'],
                 search_util.create_num_filter(model.Post.tag_count)