feat(11.1-05): add the walkthrough's admin controller, publish command and published_at migration

- make:admin-controller, make:command and make:migration output, finished:
  the Posts controller serves models.Post behind acme.blog.access_posts,
  WinterCMS-style form and list YAML embedded through pact.AdminAssets,
  blog:publish sets published_at by slug with a bound parameter
- the posts route lists published posts only, newest first
- Docker tests migrate an ICU pl-PL database, roll back published_at, serve
  the route and run blog:publish with a published and an opened database
- the page gains the admin controller, console command and added-column
  sections

docs/examples/blog/models/posts/columns.yaml

@@ -0,0 +1,10 @@
+columns:
+    title:
+        label: acme.blog::lang.posts.title_field
+        searchable: true
+    slug:
+        label: acme.blog::lang.posts.slug
+        searchable: true
+    published_at:
+        label: acme.blog::lang.posts.published_at
+        type: datetime

docs/examples/blog/models/posts/fields.yaml

@@ -0,0 +1,15 @@
+fields:
+    title:
+        label: acme.blog::lang.posts.title_field
+        type: text
+        span: left
+        required: true
+    slug:
+        label: acme.blog::lang.posts.slug
+        type: text
+        span: right
+        required: true
+    body:
+        label: acme.blog::lang.posts.body
+        type: textarea
+        size: large