[backend/database] Move emoji url generation to the Emoji entity

Iceshrimp.Backend/Core/Database/Tables/Emoji.cs

@@ -1,5 +1,6 @@
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
+using Iceshrimp.Backend.Core.Configuration;
 using Microsoft.EntityFrameworkCore;
 
 namespace Iceshrimp.Backend.Core.Database.Tables;
@@ -55,4 +56,12 @@ public class Emoji
 	/// </summary>
 	[Column("height")]
 	public int? Height { get; set; }
+	
+	public string GetPublicUri(Config.InstanceSection config) => Host == null
+		? $"https://{config.WebDomain}/emoji/{Name}"
+		: throw new Exception("Cannot access PublicUri for remote emoji");
+
+	public string? GetPublicUriOrNull(Config.InstanceSection config) => Host == null
+		? $"https://{config.WebDomain}/emoji/{Name}"
+		: null;
 }

Iceshrimp.Backend/Core/Federation/ActivityPub/ActivityRenderer.cs

@@ -97,7 +97,7 @@ public class ActivityRenderer(
 
 			var e = new ASEmoji
 			{
-				Id    = emoji.Host == null ? $"https://{config.Value.WebDomain}/emoji/{emoji.Name}" : null,
+				Id    = emoji.GetPublicUriOrNull(config.Value),
 				Name  = name,
 				Image = new ASImage { Url = new ASLink(emoji.PublicUrl) }
 			};

Iceshrimp.Backend/Core/Federation/ActivityPub/NoteRenderer.cs

@@ -75,7 +75,7 @@ public class NoteRenderer(IOptions<Config.InstanceSection> config, MfmConverter
 		               }))
 		               .Concat(emoji.Select(e => new ASEmoji
 		               {
-			               Id    = $"https://{config.Value.WebDomain}/emoji/{e.Name}",
+			               Id    = e.GetPublicUri(config.Value),
 			               Name  = e.Name,
 			               Image = new ASImage { Url = new ASLink(e.PublicUrl) }
 		               }))