feat: add jetstream config validation models

src/NATS.Server/JetStream/Validation/JetStreamConfigValidator.cs

@@ -0,0 +1,26 @@
+using NATS.Server.JetStream.Models;
+
+namespace NATS.Server.JetStream.Validation;
+
+public static class JetStreamConfigValidator
+{
+    public static ValidationResult Validate(StreamConfig config)
+        => string.IsNullOrWhiteSpace(config.Name) || config.Subjects.Count == 0
+            ? ValidationResult.Invalid("name/subjects required")
+            : ValidationResult.Valid();
+}
+
+public sealed class ValidationResult
+{
+    public bool IsValid { get; }
+    public string Message { get; }
+
+    private ValidationResult(bool isValid, string message)
+    {
+        IsValid = isValid;
+        Message = message;
+    }
+
+    public static ValidationResult Valid() => new(true, string.Empty);
+    public static ValidationResult Invalid(string message) => new(false, message);
+}