Added sample code for removing a claim using the OnTicketReceived event

Author: ProgrammerAL

astro/src/content/docs/identityserver/troubleshooting/index.mdx

@@ -301,6 +301,30 @@ services.AddAuthentication()
 
 When dealing with external authentication, you may want to implement `OnTicketReceived` to reduce the size of the cookie. This is a callback that is invoked after the external authentication process is complete. You can use this callback to remove any claims that are not needed by your solution.
 
+```csharp
+// Program.cs
+services.AddAuthentication()
+.AddOpenIdConnect("oidc", options =>
+{
+  ...
+
+  options.Events = new OpenIdConnectEvents()
+  {
+      OnTicketReceived = context =>
+      {
+          var identities = context.Principal?.Identities ?? Enumerable.Empty<ClaimsIdentity>();
+          foreach (var identity in identities)
+          {
+              var removedClaim = identity.FindFirst("unused-custom-claim");
+              _ = identity.TryRemoveClaim(removedClaim);
+          }
+
+          return Task.CompletedTask;
+      }
+  };
+});
+```
+
 ### Use Server-side Sessions
 
 You can use [server-side sessions][2] to store the