add initial chat server stuff

chat/migrations/20240116203402_init.sql

@@ -0,0 +1,51 @@
+create type instance_status as enum ('active', 'suspended');
+
+create table identity_instances (
+    id         text primary key,
+    domain     text not null unique,
+    base_url   text not null,
+    public_key text not null,
+    status     instance_status not null default 'active',
+    reason     text
+);
+
+create table users (
+    id text primary key,
+    instance_id text not null references identity_instances (id) on delete cascade,
+    remote_user_id text not null,
+    username       text not null,
+    
+    avatar text -- URL, not hash, as this is a remote file
+);
+
+create unique index users_remote_user_id_idx on users (instance_id, remote_user_id);
+create unique index users_username_idx on users (instance_id, lower(username));
+
+create table guilds (
+    id       text primary key,
+    owner_id text not null references users (id) on delete cascade,
+    name     text not null
+);
+
+create table guilds_users (
+    guild_id text not null references guilds (id) on delete cascade,
+    user_id  text not null references users (id) on delete cascade,
+
+    primary key (guild_id, user_id)
+);
+
+create table channels (
+    id       text primary key,
+    guild_id text not null references guilds (id) on delete cascade,
+    name     text not null,
+    topic    text
+);
+
+create table messages (
+    id         text primary key,
+    channel_id text not null references channels (id) on delete cascade,
+    author_id  text not null,
+    updated_at timestamptz not null default now(),
+    
+    content text not null
+);