feat(web/converse): Import repository

Imports the converse forum software I wrote a few years ago. I want to
clean this up a bit and try using Hotwire with it.

Note: The original repository was AGPL-3.0 licensed. I'm the copyright
holder and have relicensed it to GPL-3.0 in the commit that is being
merged.

Imported from: https://github.com/tazjin/converse

git-subtree-dir: web/converse
git-subtree-mainline: 386afdc794
git-subtree-split: 09168021e7
Change-Id: Ia8b587db5174ef5b3c52910d3d027199150c58e0

web/converse/migrations/2018-05-25-161939_add_closed_to_index/down.sql

@@ -0,0 +1,30 @@
+-- Update the index view:
+DROP VIEW thread_index;
+CREATE VIEW thread_index AS
+  SELECT t.id AS thread_id,
+         t.title AS title,
+         ta.name AS thread_author,
+         t.posted AS created,
+         t.sticky AS sticky,
+         p.id AS post_id,
+         pa.name AS post_author,
+         p.posted AS posted
+    FROM threads t
+    JOIN (SELECT DISTINCT ON (thread_id)
+           id, thread_id, user_id, posted
+          FROM posts
+          ORDER BY thread_id, id DESC) AS p
+    ON t.id = p.thread_id
+    JOIN users ta ON ta.id = t.user_id
+    JOIN users pa ON pa.id = p.user_id
+    ORDER BY t.sticky DESC, p.id DESC;
+
+-- Update the post view:
+DROP VIEW simple_posts;
+CREATE VIEW simple_posts AS
+  SELECT p.id AS id,
+         thread_id, body, posted, user_id,
+         users.name AS author_name,
+         users.email AS author_email
+  FROM posts p
+  JOIN users ON users.id = p.user_id;