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/up.sql

@@ -0,0 +1,83 @@
+-- This query creates a users table and migrates the existing user
+-- information (from the posts table) into it.
+
+CREATE TABLE users (
+  id SERIAL PRIMARY KEY,
+  email VARCHAR NOT NULL UNIQUE,
+  name VARCHAR NOT NULL,
+  admin BOOLEAN NOT NULL DEFAULT false
+);
+
+-- Insert the 'anonymous' user explicitly:
+INSERT INTO users (name, email)
+  VALUES ('Anonymous', 'anonymous@nothing.org');
+
+INSERT INTO users (id, email, name)
+  SELECT nextval('users_id_seq'),
+         author_email AS email,
+         author_name AS name
+  FROM posts
+  WHERE author_email != 'anonymous@nothing.org'
+  GROUP BY name, email;
+
+-- Create the 'user_id' column in the relevant tables (initially
+-- without a not-null constraint) and populate it with the data
+-- selected above:
+ALTER TABLE posts ADD COLUMN user_id INTEGER REFERENCES users (id);
+UPDATE posts SET user_id = users.id
+  FROM users
+  WHERE users.email = posts.author_email;
+
+ALTER TABLE threads ADD COLUMN user_id INTEGER REFERENCES users (id);
+UPDATE threads SET user_id = users.id
+  FROM users
+  WHERE users.email = threads.author_email;
+
+-- Add the constraints:
+ALTER TABLE posts ALTER COLUMN user_id SET NOT NULL;
+ALTER TABLE threads ALTER COLUMN user_id SET NOT NULL;
+
+-- Update the index view:
+CREATE OR REPLACE 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 search view:
+DROP MATERIALIZED VIEW search_index;
+CREATE MATERIALIZED VIEW search_index AS
+  SELECT p.id AS post_id,
+         pa.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', ta.name), 'C') ||
+         setweight(to_tsvector('simple', pa.name), 'C') AS document
+    FROM posts p
+    JOIN threads t ON t.id = p.thread_id
+    JOIN users ta ON ta.id = t.user_id
+    JOIN users pa ON pa.id = p.user_id;
+
+CREATE INDEX idx_fts_search ON search_index USING gin(document);
+
+-- And drop the old fields:
+ALTER TABLE posts DROP COLUMN author_name;
+ALTER TABLE posts DROP COLUMN author_email;
+ALTER TABLE threads DROP COLUMN author_name;
+ALTER TABLE threads DROP COLUMN author_email;