Add test for URL encoded characters

Tracing URL templates should be able to include % characters. This test
is intended to show that the current implementation needs rework in
order to handle this requirement.

spec/lib/gitlab/tracing_spec.rb

@@ -50,6 +50,7 @@ describe Gitlab::Tracing do
       true  | "https://localhost?c=%{correlation_id}"                    | "123" | "web" | "https://localhost?c=123"
       true  | "https://localhost?c=%{correlation_id}&s=%{service}"       | "123" | "web" | "https://localhost?c=123&s=web"
       true  | "https://localhost?c=%{correlation_id}"                    | nil   | "web" | "https://localhost?c="
+      true  | "https://localhost?c=%{correlation_id}&s=%22%{service}%22" | "123" | "web" | "https://localhost?c=123&s=%22web%22"
     end
 
     with_them do