Implement URL slugs (#931)

* Implement URL slugs for Users and Slots

* Fix extra spaces in slot slugs

ProjectLighthouse.Servers.Website/Extensions/SlugExtensions.cs

@@ -0,0 +1,33 @@
+using System.Text.RegularExpressions;
+using System.Web;
+using LBPUnion.ProjectLighthouse.Types.Entities.Level;
+using LBPUnion.ProjectLighthouse.Types.Entities.Profile;
+
+namespace LBPUnion.ProjectLighthouse.Servers.Website.Extensions;
+
+public static partial class SlugExtensions
+{
+    [GeneratedRegex("[^a-zA-Z0-9 ]")]
+    private static partial Regex ValidSlugCharactersRegex();
+
+    [GeneratedRegex(@"[\s]{2,}")]
+    private static partial Regex WhitespaceRegex();
+
+    /// <summary>
+    /// Generates a URL slug that only contains alphanumeric characters
+    /// with spaces replaced with dashes
+    /// </summary>
+    /// <param name="slot">The slot to generate the slug for</param>
+    /// <returns>A string containing the url slug for this slot</returns>
+    public static string GenerateSlug(this SlotEntity slot) =>
+        slot.Name.Length == 0
+            ? "unnamed-level"
+            : WhitespaceRegex().Replace(ValidSlugCharactersRegex().Replace(HttpUtility.HtmlDecode(slot.Name), ""), " ").Replace(" ", "-").ToLower();
+
+    /// <summary>
+    /// Generates a URL slug for the given user
+    /// </summary>
+    /// <param name="user">The user to generate the slug for</param>
+    /// <returns>A string containing the url slug for this user</returns>
+    public static string GenerateSlug(this UserEntity user) => user.Username.ToLower();
+}