Extract date rendering into per-feature Date components

Elternbeirat.Web/Features/Posts/PostDate.razor.cs

@@ -0,0 +1,18 @@
+using Microsoft.AspNetCore.Components;
+
+namespace Elternbeirat.Web.Features.Posts;
+
+/// <summary>
+///     Renders a post's publication day as a <c>&lt;time&gt;</c> element, in both a
+///     machine-readable and a visitor-facing form. The two formats come from
+///     <see cref="PostDateFormat"/>.
+/// </summary>
+public partial class PostDate
+{
+    /// <summary>
+    ///     The post's publication day.
+    /// </summary>
+    [Parameter]
+    [EditorRequired]
+    public DateOnly Value { get; set; }
+}