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.Concelier.Storage.Mongo.Tests/AdvisoryConflictStoreTests.cs

@@ -0,0 +1,82 @@
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using MongoDB.Bson;
+using MongoDB.Driver;
+using StellaOps.Concelier.Storage.Mongo;
+using StellaOps.Concelier.Storage.Mongo.Conflicts;
+using StellaOps.Concelier.Testing;
+using Xunit;
+
+namespace StellaOps.Concelier.Storage.Mongo.Tests;
+
+[Collection("mongo-fixture")]
+public sealed class AdvisoryConflictStoreTests
+{
+    private readonly IMongoDatabase _database;
+
+    public AdvisoryConflictStoreTests(MongoIntegrationFixture fixture)
+    {
+        _database = fixture.Database ?? throw new ArgumentNullException(nameof(fixture.Database));
+    }
+
+    [Fact]
+    public async Task InsertAndRetrieve_PersistsConflicts()
+    {
+        var store = new AdvisoryConflictStore(_database);
+        var vulnerabilityKey = $"CVE-{Guid.NewGuid():N}";
+        var baseTime = DateTimeOffset.UtcNow;
+        var statementIds = new[] { Guid.NewGuid(), Guid.NewGuid() };
+
+        var conflict = new AdvisoryConflictRecord(
+            Guid.NewGuid(),
+            vulnerabilityKey,
+            new byte[] { 0x10, 0x20 },
+            baseTime,
+            baseTime.AddSeconds(30),
+            statementIds,
+            new BsonDocument("explanation", "first-pass"));
+
+        await store.InsertAsync(new[] { conflict }, CancellationToken.None);
+
+        var results = await store.GetConflictsAsync(vulnerabilityKey, null, CancellationToken.None);
+
+        Assert.Single(results);
+        Assert.Equal(conflict.Id, results[0].Id);
+        Assert.Equal(statementIds, results[0].StatementIds);
+    }
+
+    [Fact]
+    public async Task GetConflicts_AsOfFilters()
+    {
+        var store = new AdvisoryConflictStore(_database);
+        var vulnerabilityKey = $"CVE-{Guid.NewGuid():N}";
+        var baseTime = DateTimeOffset.UtcNow;
+
+        var earlyConflict = new AdvisoryConflictRecord(
+            Guid.NewGuid(),
+            vulnerabilityKey,
+            new byte[] { 0x01 },
+            baseTime,
+            baseTime.AddSeconds(10),
+            new[] { Guid.NewGuid() },
+            new BsonDocument("stage", "early"));
+
+        var lateConflict = new AdvisoryConflictRecord(
+            Guid.NewGuid(),
+            vulnerabilityKey,
+            new byte[] { 0x02 },
+            baseTime.AddMinutes(10),
+            baseTime.AddMinutes(10).AddSeconds(15),
+            new[] { Guid.NewGuid() },
+            new BsonDocument("stage", "late"));
+
+        await store.InsertAsync(new[] { earlyConflict, lateConflict }, CancellationToken.None);
+
+        var results = await store.GetConflictsAsync(vulnerabilityKey, baseTime.AddMinutes(1), CancellationToken.None);
+
+        Assert.Single(results);
+        Assert.Equal("early", results[0].Details["stage"].AsString);
+    }
+}