[Instrumentation.Hangfire] Fix analysis warnings (#964)

Fix/suppress code analysis warnings in OpenTelemetry.Instrumentation.Hangfire.
Contributes to #950.

src/OpenTelemetry.Instrumentation.Hangfire/Implementation/HangfireInstrumentationJobFilterAttribute.cs

@@ -28,7 +28,7 @@ namespace OpenTelemetry.Instrumentation.Hangfire.Implementation;
 using OpenTelemetry.Context.Propagation;
 using OpenTelemetry.Trace;
 
-internal class HangfireInstrumentationJobFilterAttribute : JobFilterAttribute, IServerFilter, IClientFilter
+internal sealed class HangfireInstrumentationJobFilterAttribute : JobFilterAttribute, IServerFilter, IClientFilter
 {
     private readonly HangfireInstrumentationOptions options;
 
@@ -37,6 +37,8 @@ public HangfireInstrumentationJobFilterAttribute(HangfireInstrumentationOptions
         this.options = options;
     }
 
+    public HangfireInstrumentationOptions Options { get; }
+
     public void OnPerforming(PerformingContext performingContext)
     {
         // Short-circuit if nobody is listening
@@ -123,7 +125,7 @@ private static void InjectActivityProperties(IDictionary<string, string> jobPara
 
     private static IEnumerable<string> ExtractActivityProperties(Dictionary<string, string> telemetryData, string key)
     {
-        return telemetryData.ContainsKey(key) ? new[] { telemetryData[key] } : Enumerable.Empty<string>();
+        return telemetryData.TryGetValue(key, out var value) ? new[] { value } : Enumerable.Empty<string>();
     }
 
     private void SetStatusAndRecordException(Activity activity, Exception exception)