feat: rewrite database schema for localized autoproxy

PluralKit.Core/Database/Migrations/27.sql

@@ -0,0 +1,36 @@
+-- schema version 27
+-- autoproxy locations
+
+-- mode pseudo-enum: (copied from 3.sql)
+-- 1 = autoproxy off
+-- 2 = front mode (first fronter)
+-- 3 = latch mode (last proxyer)
+-- 4 = member mode (specific member)
+
+create table autoproxy (
+    system int references systems(id) on delete cascade,
+    channel_id bigint,
+    guild_id bigint,
+    autoproxy_mode int check (mode in (1, 2, 3, 4)) not null default 1,
+    autoproxy_member int references members(id) on delete set null,
+    last_latch_timestamp timestamp,
+    check (
+        (channel_id  = 0 and guild_id  = 0)
+     or (channel_id != 0 and guild_id  = 0)
+     or (channel_id  = 0 and guild_id != 0)
+    ),
+    primary key (system, channel_id, guild_id)
+);
+
+insert into autoproxy select
+    system,
+    0 as channel_id,
+    guild as guild_id,
+    autoproxy_mode,
+    autoproxy_member
+from system_guild;
+
+alter table system_guild drop column autoproxy_mode;
+alter table system_guild drop column autoproxy_member;
+
+update info set schema_version = 27;