Add group icon and privacy to the database schema

PluralKit.Core/Database/Migrations/9.sql

@@ -1,11 +1,20 @@
 -- SCHEMA VERSION 9: 2020-xx-xx --
+-- Adds support for member groups.
 
 create table groups (
     id int primary key generated always as identity,
     hid char(5) unique not null,
     system int not null references systems(id) on delete cascade,
+    
     name text not null,
     description text,
+    icon text,
+    
+    -- Description columns follow the same pattern as usual: 1 = public, 2 = private
+    description_privacy integer check (description_privacy in (1, 2)) not null default 1,
+    icon_privacy integer check (icon_privacy in (1, 2)) not null default 1,
+    visibility integer check (visibility in (1, 2)) not null default 1,
+
     created timestamp with time zone not null default (current_timestamp at time zone 'utc')
 );