Added logging.

JSMR.Application/Logging/LogObjectBuilder.cs

@@ -0,0 +1,36 @@
+namespace JSMR.Application.Logging;
+
+public sealed class LogObjectBuilder
+{
+    private readonly Dictionary<string, object> _d = [];
+
+    public LogObjectBuilder Add(string key, object? value)
+    {
+        if (value is null)
+            return this;
+
+        _d[key] = value;
+
+        return this;
+    }
+
+    public LogObjectBuilder AddIfNotEmpty(string key, string? value)
+        => string.IsNullOrWhiteSpace(value) ? this : Add(key, value);
+
+    public LogObjectBuilder AddIfNotEmpty<T>(string key, IReadOnlyCollection<T>? value, int? preview = null)
+    {
+        if (value is null || value.Count == 0)
+            return this;
+
+        if (preview is null || value.Count <= preview)
+            return Add(key, value);
+
+        // Store small preview + count so logs stay compact
+        return Add(key, new { Preview = value.Take(preview.Value), value.Count });
+    }
+
+    public LogObjectBuilder AddIfNotDefault<T>(string key, T value) where T : struct, IEquatable<T>
+        => value.Equals(default) ? this : Add(key, value);
+
+    public object Build() => _d;
+}