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.Attestor/StellaOps.Attestor.Infrastructure/Storage/MongoAttestorEntryRepository.cs

@@ -76,6 +76,9 @@ internal sealed class MongoAttestorEntryRepository : IAttestorEntryRepository
         [BsonElement("signerIdentity")]
         public SignerIdentityDocument SignerIdentity { get; set; } = new();
 
+        [BsonElement("mirror")]
+        public MirrorDocument? Mirror { get; set; }
+
         public static AttestorEntryDocument FromDomain(AttestorEntry entry)
         {
             return new AttestorEntryDocument
@@ -109,6 +112,7 @@ internal sealed class MongoAttestorEntryRepository : IAttestorEntryRepository
                 },
                 Log = new LogDocument
                 {
+                    Backend = entry.Log.Backend,
                     Url = entry.Log.Url,
                     LogId = entry.Log.LogId
                 },
@@ -120,7 +124,8 @@ internal sealed class MongoAttestorEntryRepository : IAttestorEntryRepository
                     Issuer = entry.SignerIdentity.Issuer,
                     SubjectAlternativeName = entry.SignerIdentity.SubjectAlternativeName,
                     KeyId = entry.SignerIdentity.KeyId
-                }
+                },
+                Mirror = entry.Mirror is null ? null : MirrorDocument.FromDomain(entry.Mirror)
             };
         }
 
@@ -155,6 +160,7 @@ internal sealed class MongoAttestorEntryRepository : IAttestorEntryRepository
                 },
                 Log = new AttestorEntry.LogDescriptor
                 {
+                    Backend = Log.Backend,
                     Url = Log.Url,
                     LogId = Log.LogId
                 },
@@ -166,7 +172,8 @@ internal sealed class MongoAttestorEntryRepository : IAttestorEntryRepository
                     Issuer = SignerIdentity.Issuer,
                     SubjectAlternativeName = SignerIdentity.SubjectAlternativeName,
                     KeyId = SignerIdentity.KeyId
-                }
+                },
+                Mirror = Mirror?.ToDomain()
             };
         }
 
@@ -220,6 +227,9 @@ internal sealed class MongoAttestorEntryRepository : IAttestorEntryRepository
 
         internal sealed class LogDocument
         {
+            [BsonElement("backend")]
+            public string Backend { get; set; } = "primary";
+
             [BsonElement("url")]
             public string Url { get; set; } = string.Empty;
 
@@ -241,5 +251,92 @@ internal sealed class MongoAttestorEntryRepository : IAttestorEntryRepository
             [BsonElement("kid")]
             public string? KeyId { get; set; }
         }
+
+        internal sealed class MirrorDocument
+        {
+            [BsonElement("backend")]
+            public string Backend { get; set; } = string.Empty;
+
+            [BsonElement("url")]
+            public string Url { get; set; } = string.Empty;
+
+            [BsonElement("uuid")]
+            public string? Uuid { get; set; }
+
+            [BsonElement("index")]
+            public long? Index { get; set; }
+
+            [BsonElement("status")]
+            public string Status { get; set; } = "pending";
+
+            [BsonElement("proof")]
+            public ProofDocument? Proof { get; set; }
+
+            [BsonElement("logId")]
+            public string? LogId { get; set; }
+
+            [BsonElement("error")]
+            public string? Error { get; set; }
+
+            public static MirrorDocument FromDomain(AttestorEntry.LogReplicaDescriptor mirror)
+            {
+                return new MirrorDocument
+                {
+                    Backend = mirror.Backend,
+                    Url = mirror.Url,
+                    Uuid = mirror.Uuid,
+                    Index = mirror.Index,
+                    Status = mirror.Status,
+                    Proof = mirror.Proof is null ? null : new ProofDocument
+                    {
+                        Checkpoint = mirror.Proof.Checkpoint is null ? null : new CheckpointDocument
+                        {
+                            Origin = mirror.Proof.Checkpoint.Origin,
+                            Size = mirror.Proof.Checkpoint.Size,
+                            RootHash = mirror.Proof.Checkpoint.RootHash,
+                            Timestamp = mirror.Proof.Checkpoint.Timestamp is null
+                                ? null
+                                : BsonDateTime.Create(mirror.Proof.Checkpoint.Timestamp.Value)
+                        },
+                        Inclusion = mirror.Proof.Inclusion is null ? null : new InclusionDocument
+                        {
+                            LeafHash = mirror.Proof.Inclusion.LeafHash,
+                            Path = mirror.Proof.Inclusion.Path
+                        }
+                    },
+                    LogId = mirror.LogId,
+                    Error = mirror.Error
+                };
+            }
+
+            public AttestorEntry.LogReplicaDescriptor ToDomain()
+            {
+                return new AttestorEntry.LogReplicaDescriptor
+                {
+                    Backend = Backend,
+                    Url = Url,
+                    Uuid = Uuid,
+                    Index = Index,
+                    Status = Status,
+                    Proof = Proof is null ? null : new AttestorEntry.ProofDescriptor
+                    {
+                        Checkpoint = Proof.Checkpoint is null ? null : new AttestorEntry.CheckpointDescriptor
+                        {
+                            Origin = Proof.Checkpoint.Origin,
+                            Size = Proof.Checkpoint.Size,
+                            RootHash = Proof.Checkpoint.RootHash,
+                            Timestamp = Proof.Checkpoint.Timestamp?.ToUniversalTime()
+                        },
+                        Inclusion = Proof.Inclusion is null ? null : new AttestorEntry.InclusionDescriptor
+                        {
+                            LeafHash = Proof.Inclusion.LeafHash,
+                            Path = Proof.Inclusion.Path
+                        }
+                    },
+                    LogId = LogId,
+                    Error = Error
+                };
+            }
+        }
     }
 }