admin: Add support for comment search by Thread URL in admin interface

See:
- isso-comments#642
- isso-comments#1000

isso/templates/admin.html

@@ -74,9 +74,9 @@ <h2>Administration</h2>
           <div class="search">
             <form action="/admin/" method="get">
               <input type="hidden" name="mode" value="0" />
-              <label>Comment search URL
-                <input type="search" class="search__input" name="comment_search_url" value="{{comment_search_url}}" spellcheck="false"
-                  required placeholder="Comment or Thread URL" />
+              <label>Search by URL
+                <input type="url" class="search__input" name="comment_search_url" value="{{comment_search_url}}" spellcheck="false"
+                  required placeholder="https://example.com/demo/#isso-1" />
               </label>
               <button type="submit" class="search__button">Search</button>
             </form>

isso/views/comments.py

@@ -1428,7 +1428,9 @@ def login(self, env, req):
     @apiQuery {Number{0,1}} [asc=0]
         Ascending
     @apiQuery {String} comment_search_url
-        Search comments by URL
+        Search comments by URL. Both threads and individual comments are valid.
+        For example, a thread might have a URL like 'http://example.com/thread'
+        and an individual comment might have a URL like 'http://example.com/thread#isso-1'
 
     @apiExample {curl} Listing of published comments:
         curl 'https://comments.example.com/admin/?mode=1&page=0&order_by=modified&asc=1' -b cookie.txt