fix: Allow for 2 seconds clock skew in token validation (#536)

Due to slightly mismatched clocks, tokens from the tokengenerator (or
other sources) might create tokens that are not yet valid (when
validation `iat` claim) in Dialogporten. We can alleviate this by
allowing for 2 seconds of skew.

src/Digdir.Domain.Dialogporten.WebApi/Common/Authentication/AuthenticationBuilderExtensions.cs

@@ -38,7 +38,7 @@ public static IServiceCollection AddDialogportenAuthentication(
                     ValidateAudience = false,
                     RequireExpirationTime = true,
                     ValidateLifetime = true,
-                    ClockSkew = TimeSpan.Zero
+                    ClockSkew = TimeSpan.FromSeconds(2)
                 };
 
                 options.Events = new JwtBearerEvents