Implement MongoDB-based storage for Pack Run approval, artifact, log, and state management

- Added MongoPackRunApprovalStore for managing approval states with MongoDB.
- Introduced MongoPackRunArtifactUploader for uploading and storing artifacts.
- Created MongoPackRunLogStore to handle logging of pack run events.
- Developed MongoPackRunStateStore for persisting and retrieving pack run states.
- Implemented unit tests for MongoDB stores to ensure correct functionality.
- Added MongoTaskRunnerTestContext for setting up MongoDB test environment.
- Enhanced PackRunStateFactory to correctly initialize state with gate reasons.

src/TaskRunner/StellaOps.TaskRunner/StellaOps.TaskRunner.Tests/MongoTaskRunnerTestContext.cs

@@ -0,0 +1,89 @@
+using Mongo2Go;
+using MongoDB.Driver;
+using StellaOps.TaskRunner.Core.Configuration;
+using StellaOps.Testing;
+using Xunit;
+
+namespace StellaOps.TaskRunner.Tests;
+
+internal sealed class MongoTaskRunnerTestContext : IAsyncDisposable, IDisposable
+{
+    private readonly MongoDbRunner? runner;
+    private readonly string databaseName;
+    private readonly IMongoClient client;
+    private readonly string connectionString;
+
+    private MongoTaskRunnerTestContext(
+        IMongoClient client,
+        IMongoDatabase database,
+        MongoDbRunner? runner,
+        string databaseName,
+        string connectionString)
+    {
+        this.client = client;
+        Database = database;
+        this.runner = runner;
+        this.databaseName = databaseName;
+        this.connectionString = connectionString;
+    }
+
+    public IMongoDatabase Database { get; }
+
+    public static MongoTaskRunnerTestContext Create()
+    {
+        OpenSslLegacyShim.EnsureOpenSsl11();
+
+        var uri = Environment.GetEnvironmentVariable("STELLAOPS_TEST_MONGO_URI");
+        if (!string.IsNullOrWhiteSpace(uri))
+        {
+            try
+            {
+                var url = MongoUrl.Create(uri);
+                var client = new MongoClient(url);
+                var databaseName = string.IsNullOrWhiteSpace(url.DatabaseName)
+                    ? $"taskrunner-tests-{Guid.NewGuid():N}"
+                    : url.DatabaseName;
+                var database = client.GetDatabase(databaseName);
+                return new MongoTaskRunnerTestContext(client, database, runner: null, databaseName, uri);
+            }
+            catch (Exception ex)
+            {
+                Assert.Skip($"Failed to connect to MongoDB using STELLAOPS_TEST_MONGO_URI: {ex.Message}");
+                throw new InvalidOperationException(); // Unreachable
+            }
+        }
+
+        try
+        {
+            var runner = MongoDbRunner.Start(singleNodeReplSet: false);
+            var client = new MongoClient(runner.ConnectionString);
+            var databaseName = $"taskrunner-tests-{Guid.NewGuid():N}";
+            var database = client.GetDatabase(databaseName);
+            return new MongoTaskRunnerTestContext(client, database, runner, databaseName, runner.ConnectionString);
+        }
+        catch (Exception ex)
+        {
+            Assert.Skip($"Unable to start embedded MongoDB (Mongo2Go): {ex.Message}");
+            throw new InvalidOperationException(); // Unreachable
+        }
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        await client.DropDatabaseAsync(databaseName);
+        runner?.Dispose();
+    }
+
+    public void Dispose()
+    {
+        client.DropDatabase(databaseName);
+        runner?.Dispose();
+    }
+
+    public TaskRunnerMongoOptions CreateMongoOptions()
+        => new()
+        {
+            ConnectionString = connectionString,
+            Database = databaseName
+        };
+}