feat: split ignores into 'ignore messages' and 'ignore entities'

Catalogger.Backend/Database/Migrations/004_split_message_config.up.sql

@@ -0,0 +1,12 @@
+alter table guilds
+    add column messages jsonb not null default '{}';
+
+-- Extract the current message-related configuration options into the new "messages" column
+-- noinspection SqlWithoutWhere
+update guilds
+set messages = jsonb_build_object('IgnoredUsers', channels['IgnoredUsers'], 'IgnoredChannels',
+                                  channels['IgnoredChannels'], 'IgnoredUsersPerChannel',
+                                  channels['IgnoredUsersPerChannel']);
+
+-- We don't update the "channels" column as it will be cleared out automatically over time,
+-- as channel configurations are updated by the bot