feat: add short IDs + link shortener

scripts/migrate/018_short_ids.sql

@@ -0,0 +1,50 @@
+-- +migrate Up
+
+-- 2023-06-03: Add short IDs for the prns.cc domain.
+
+-- add the columns
+alter table users add column sid text unique check(length(sid)=5);
+alter table members add column sid text unique check(length(sid)=6);
+alter table users add column last_sid_reroll timestamptz not null default now() - '1 hour'::interval;
+
+-- create the generate short ID functions
+-- these are copied from PluralKit's HID functions:
+-- https://github.com/PluralKit/PluralKit/blob/e4a2930bf353af9406e48934569677d7de6dd90d/PluralKit.Core/Database/Functions/functions.sql#L118-L152
+
+-- +migrate StatementBegin
+create function generate_sid(len int) returns text as $$
+    select string_agg(substr('abcdefghijklmnopqrstuvwxyz', ceil(random() * 26)::integer, 1), '') from generate_series(1, len)
+$$ language sql volatile;
+-- +migrate StatementEnd
+
+-- +migrate StatementBegin
+create function find_free_user_sid() returns text as $$
+declare new_sid text;
+begin
+    loop
+        new_sid := generate_sid(5);
+        if not exists (select 1 from users where sid = new_sid) then return new_sid; end if;
+    end loop;
+end
+$$ language plpgsql volatile;
+-- +migrate StatementEnd
+
+-- +migrate StatementBegin
+create function find_free_member_sid() returns text as $$
+declare new_sid text;
+begin
+    loop
+        new_sid := generate_sid(6);
+        if not exists (select 1 from members where sid = new_sid) then return new_sid; end if;
+    end loop;
+end
+$$ language plpgsql volatile;
+-- +migrate StatementEnd
+
+-- give all users and members short IDs
+update users set sid = find_free_user_sid();
+update members set sid = find_free_member_sid();
+
+-- finally, make the values non-nullable
+alter table users alter column sid set not null;
+alter table members alter column sid set not null;