Add channel test providers for Email, Slack, Teams, and Webhook

- Implemented EmailChannelTestProvider to generate email preview payloads.
- Implemented SlackChannelTestProvider to create Slack message previews.
- Implemented TeamsChannelTestProvider for generating Teams Adaptive Card previews.
- Implemented WebhookChannelTestProvider to create webhook payloads.
- Added INotifyChannelTestProvider interface for channel-specific preview generation.
- Created ChannelTestPreviewContracts for request and response models.
- Developed NotifyChannelTestService to handle test send requests and generate previews.
- Added rate limit policies for test sends and delivery history.
- Implemented unit tests for service registration and binding.
- Updated project files to include necessary dependencies and configurations.

src/StellaOps.Authority/StellaOps.Authority.Storage.Mongo/Documents/AuthorityTokenDocument.cs

@@ -62,6 +62,18 @@ public sealed class AuthorityTokenDocument
     [BsonIgnoreIfNull]
     public string? RevokedReasonDescription { get; set; }
 
+    [BsonElement("senderConstraint")]
+    [BsonIgnoreIfNull]
+    public string? SenderConstraint { get; set; }
+
+    [BsonElement("senderKeyThumbprint")]
+    [BsonIgnoreIfNull]
+    public string? SenderKeyThumbprint { get; set; }
+
+    [BsonElement("senderNonce")]
+    [BsonIgnoreIfNull]
+    public string? SenderNonce { get; set; }
+
 
     [BsonElement("devices")]
     [BsonIgnoreIfNull]

src/StellaOps.Authority/StellaOps.Authority.Storage.Mongo/Initialization/AuthorityTokenCollectionInitializer.cs

@@ -27,7 +27,13 @@ internal sealed class AuthorityTokenCollectionInitializer : IAuthorityCollection
                 Builders<AuthorityTokenDocument>.IndexKeys
                     .Ascending(t => t.Status)
                     .Ascending(t => t.RevokedAt),
-                new CreateIndexOptions<AuthorityTokenDocument> { Name = "token_status_revokedAt" })
+                new CreateIndexOptions<AuthorityTokenDocument> { Name = "token_status_revokedAt" }),
+            new(
+                Builders<AuthorityTokenDocument>.IndexKeys.Ascending(t => t.SenderConstraint),
+                new CreateIndexOptions<AuthorityTokenDocument> { Name = "token_sender_constraint", Sparse = true }),
+            new(
+                Builders<AuthorityTokenDocument>.IndexKeys.Ascending(t => t.SenderKeyThumbprint),
+                new CreateIndexOptions<AuthorityTokenDocument> { Name = "token_sender_thumbprint", Sparse = true })
         };
 
         var expirationFilter = Builders<AuthorityTokenDocument>.Filter.Exists(t => t.ExpiresAt, true);