feat: complete jetstream deep operational parity closure

tests/NATS.Server.Tests/JetStream/JetStreamFileStoreCompressionEncryptionParityTests.cs

@@ -0,0 +1,55 @@
+using System.Text;
+using System.Text.Json;
+using NATS.Server.JetStream.Storage;
+
+namespace NATS.Server.Tests;
+
+public class JetStreamFileStoreCompressionEncryptionParityTests
+{
+    [Fact]
+    public async Task Compression_and_encryption_roundtrip_is_versioned_and_detects_wrong_key_corruption()
+    {
+        var dir = Path.Combine(Path.GetTempPath(), $"nats-js-fs-crypto-{Guid.NewGuid():N}");
+        var options = new FileStoreOptions
+        {
+            Directory = dir,
+            EnableCompression = true,
+            EnableEncryption = true,
+            EncryptionKey = [1, 2, 3, 4],
+        };
+
+        try
+        {
+            ulong sequence;
+            await using (var store = new FileStore(options))
+            {
+                sequence = await store.AppendAsync("orders.created", Encoding.UTF8.GetBytes("payload"), default);
+                var loaded = await store.LoadAsync(sequence, default);
+                loaded.ShouldNotBeNull();
+                Encoding.UTF8.GetString(loaded.Payload.ToArray()).ShouldBe("payload");
+            }
+
+            var firstLine = File.ReadLines(Path.Combine(dir, "messages.jsonl")).First();
+            var payloadBase64 = JsonDocument.Parse(firstLine).RootElement.GetProperty("PayloadBase64").GetString();
+            payloadBase64.ShouldNotBeNull();
+            var persisted = Convert.FromBase64String(payloadBase64!);
+            persisted.Take(4).SequenceEqual("FSV1"u8.ToArray()).ShouldBeTrue();
+
+            Should.Throw<InvalidDataException>(() =>
+            {
+                _ = new FileStore(new FileStoreOptions
+                {
+                    Directory = dir,
+                    EnableCompression = true,
+                    EnableEncryption = true,
+                    EncryptionKey = [9, 9, 9, 9],
+                });
+            });
+        }
+        finally
+        {
+            if (Directory.Exists(dir))
+                Directory.Delete(dir, recursive: true);
+        }
+    }
+}