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/2018-05-01-141548_add-users/down.sql

@@ -0,0 +1,63 @@
+-- First restore the old columns:
+ALTER TABLE threads ADD COLUMN author_name VARCHAR;
+ALTER TABLE threads ADD COLUMN author_email VARCHAR;
+ALTER TABLE posts ADD COLUMN author_name VARCHAR;
+ALTER TABLE posts ADD COLUMN author_email VARCHAR;
+
+-- Then select the data back into them:
+UPDATE threads SET author_name = users.name,
+                   author_email = users.email
+  FROM users
+  WHERE threads.user_id = users.id;
+
+UPDATE posts SET author_name = users.name,
+                 author_email = users.email
+  FROM users
+  WHERE posts.user_id = users.id;
+
+-- add the constraints back:
+ALTER TABLE threads ALTER COLUMN author_name SET NOT NULL;
+ALTER TABLE threads ALTER COLUMN author_email SET NOT NULL;
+ALTER TABLE posts ALTER COLUMN author_name SET NOT NULL;
+ALTER TABLE posts ALTER COLUMN author_email SET NOT NULL;
+
+-- reset the index view:
+CREATE OR REPLACE VIEW thread_index AS
+  SELECT t.id AS thread_id,
+         t.title AS title,
+         t.author_name AS thread_author,
+         t.posted AS created,
+         t.sticky AS sticky,
+         p.id AS post_id,
+         p.author_name AS post_author,
+         p.posted AS posted
+    FROM threads t
+    JOIN (SELECT DISTINCT ON (thread_id)
+           id, thread_id, author_name, posted
+          FROM posts
+          ORDER BY thread_id, id DESC) AS p
+    ON t.id = p.thread_id
+    ORDER BY t.sticky DESC, p.id DESC;
+
+-- reset the search view:
+DROP MATERIALIZED VIEW search_index;
+CREATE MATERIALIZED VIEW search_index AS
+  SELECT p.id AS post_id,
+         p.author_name AS author,
+         t.id AS thread_id,
+         t.title AS title,
+         p.body AS body,
+         setweight(to_tsvector('english', t.title), 'B') ||
+         setweight(to_tsvector('english', p.body), 'A') ||
+         setweight(to_tsvector('simple', t.author_name), 'C') ||
+         setweight(to_tsvector('simple', p.author_name), 'C') AS document
+    FROM posts p
+    JOIN threads t
+    ON t.id = p.thread_id;
+
+CREATE INDEX idx_fts_search ON search_index USING gin(document);
+
+-- and drop the users table and columns:
+ALTER TABLE posts DROP COLUMN user_id;
+ALTER TABLE threads DROP COLUMN user_id;
+DROP TABLE users;