feat(web/panettone): Add a system for database migrations

Add a system for writing, running, and tracking database
migrations (changes to the database schema) over time, inspired by but
significantly simpler than postmodern-passenger-pigeon.

Migrations can be generated by
running (PANETTONE.MODEL:GENERATE-MIGRATION "name"), and are numerically
ordered lisp files that define (at least) a function called UP, which
runs the migration. The migrations that have been run against the
database are tracked in the `migrations` table, and when the
`(PANETTONE.MODEL:MIGRATE)` function is called (as it is on startup),
all migrations that have not yet been run are run within a transaction.

This includes one migration `1-init-schema.lisp`, which migrates the
database (idempotently) to the current state of the schema.

Change-Id: Id243a47763abea649784b12f25a6d05c2267381c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11253
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

web/panettone/default.nix

@@ -1,4 +1,4 @@
-{ depot, ... }:
+{ depot, pkgs, ... }:
 
 depot.nix.buildLisp.program {
   name = "panettone";
@@ -9,6 +9,7 @@ depot.nix.buildLisp.program {
     cl-ppcre
     cl-smtp
     cl-who
+    str
     defclass-std
     drakma
     easy-routes
@@ -23,6 +24,14 @@ depot.nix.buildLisp.program {
   srcs = [
     ./panettone.asd
     ./src/packages.lisp
+    (pkgs.writeText "build.lisp" ''
+      (defpackage build
+        (:use :cl :alexandria)
+        (:export :*migrations-dir*))
+      (in-package :build)
+      (declaim (optimize (safety 3)))
+      (defvar *migrations-dir* "${./src/migrations}")
+    '')
     ./src/util.lisp
     ./src/css.lisp
     ./src/email.lisp