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/src/packages.lisp

@@ -36,16 +36,16 @@
   (:import-from :alexandria :if-let :when-let :define-constant)
   (:export
    :prepare-db-connections
-   :ddl/init
+   :migrate
    :*pg-spec*
 
    :user-settings
    :user-dn :enable-email-notifications-p :settings-for-user
    :update-user-settings :enable-email-notifications
 
-   :issue :issue-comment :issue-event
+   :issue :issue-comment :issue-event :migration
    :id :subject :body :author-dn :issue-id :status :created-at :acting-user-dn
-   :field :previous-value :new-value
+   :field :previous-value :new-value :+issue-statuses+
 
    :get-issue :issue-exists-p :list-issues :create-issue :set-issue-status
    :update-issue :delete-issue :issue-not-found :not-found-id