Harden the content contracts and enforce the slug rule

Elternbeirat.Contracts/Faq.cs

@@ -13,30 +13,41 @@ public record Faq
     /// <summary>
     ///     Gets the PocketBase record id.
     /// </summary>
+    /// <remarks>
+    ///     <see langword="required"/>: every stored record has an id. Modeling it as
+    ///     required states which fields a record must carry, independent of the store,
+    ///     so a future data source has to supply them too.
+    /// </remarks>
     [JsonPropertyName("id")]
-    public string Id { get; init; } = "";
+    public required string Id { get; init; }
 
     /// <summary>
     ///     Gets the question as a parent would phrase it.
     /// </summary>
+    /// <remarks>
+    ///     <see langword="required"/>: a FAQ entry without a question is incomplete, and
+    ///     the field is required in PocketBase.
+    /// </remarks>
     [JsonPropertyName("question")]
-    public string Question { get; init; } = "";
+    public required string Question { get; init; }
 
     /// <summary>
     ///     Gets the answer as Markdown.
     /// </summary>
+    /// <remarks>
+    ///     <see langword="required"/>: a FAQ entry exists to answer its question, so an
+    ///     entry without an answer is incomplete. The field is required in PocketBase.
+    /// </remarks>
     [JsonPropertyName("answer")]
-    public string Answer { get; init; } = "";
+    public required string Answer { get; init; }
 
     /// <summary>
     ///     Gets the topic the question is grouped under, e.g. <c>"mensa"</c>.
     /// </summary>
+    /// <remarks>
+    ///     <see langword="required"/>: the FAQ page groups entries by topic, so an entry
+    ///     without one has no place. The field is required in PocketBase.
+    /// </remarks>
     [JsonPropertyName("topic")]
-    public string Topic { get; init; } = "";
-
-    /// <summary>
-    ///     Gets a value indicating whether the question is visible to visitors of the site.
-    /// </summary>
-    [JsonPropertyName("public")]
-    public bool Public { get; init; }
+    public required string Topic { get; init; }
 }