Add attachment list API

extra/admin-api/Models/Spacebar.Models.Api/CreateAttachmentRequest.cs

@@ -1,4 +1,5 @@
 using System.Text.Json.Serialization;
+using Spacebar.Models.Generic;
 
 namespace Spacebar.Models.Api;
 
@@ -38,4 +39,20 @@ public class CreateAttachmentResponse {
         [JsonPropertyName("original_content_type")]
         public string? OriginalContentType { get; set; }
     }
+}
+
+public class AttachmentListResponse {
+    [JsonPropertyName("total")]
+    public int Total { get; set; }
+
+    [JsonPropertyName("items")]
+    public List<Entry> Items { get; set; }
+
+    public class Entry {
+        [JsonPropertyName("attachment")]
+        public MessageAttachment Attachment { get; set; }
+
+        [JsonPropertyName("message_reference")]
+        public MessageReference MessageReference { get; set; }
+    }
 }

extra/admin-api/Models/Spacebar.Models.Api/Spacebar.Models.Api.csproj

@@ -6,4 +6,9 @@
         <Nullable>enable</Nullable>
     </PropertyGroup>
 
+    <ItemGroup>
+        <ProjectReference Include="..\Spacebar.Models.Generic\Spacebar.Models.Generic.csproj" Condition="'$(ContinuousIntegrationBuild)'!='true'"/>
+        <PackageReference Include="Spacebar.Models.Generic" Version="*-preview*" Condition="'$(ContinuousIntegrationBuild)'=='true'"/>
+    </ItemGroup>
+
 </Project>