Expose Session Id via Backtrace Metrics (#238)

* Expose Session Id via Backtrace Metrics

* Drop readonly

---------

Co-authored-by: Konrad Dysput <konrad.dysput@saucelabs.com>

Author: konraddysput

Runtime/Interfaces/IBacktraceMetrics.cs

@@ -1,5 +1,6 @@
 using Backtrace.Unity.Model.Attributes;
 using Backtrace.Unity.Model.Metrics;
+using System;
 using System.Collections.Generic;
 
 namespace Backtrace.Unity.Interfaces
@@ -22,6 +23,11 @@ public interface IBacktraceMetrics : IScopeAttributeProvider
         /// </summary>
         uint MaximumSummedEvents { get; set; }
 
+        /// <summary>
+        /// Current session Id
+        /// </summary>
+        Guid SessionId { get; }
+
         /// <summary>
         /// Maximum number of unique events in store. If number of events in store hit the limit
         /// BacktraceMetrics instance will send data to Backtrace.

Runtime/Services/BacktraceMetrics.cs

@@ -16,7 +16,7 @@ internal sealed class BacktraceMetrics : IBacktraceMetrics
         /// <summary>
         /// Session Id
         /// </summary>
-        public readonly Guid SessionId = Guid.NewGuid();
+        public Guid SessionId { get; } = Guid.NewGuid();
 
         /// <summary>
         /// Default submission URL