Improve error message when adding a related issue as a Guest

Summary

As of %13.11, when you try adding a related issue as a project Guest, you get an error message, edited in !45064 (merged):

No matching issue found. Make sure that you are adding a valid issue URL.

Origin: comment #227630 (comment 405101021):

The No Issue found for given params message is also displayed when trying to create an issue reference to a an issue in a project you are not a member of.
Would have been nice if the message included a hint that you need to be a level greater than Guest in the project of the issue.

Possible fixes

Add a specific message for this scenario, for example:

No matching issue found. To add an issue, you must at least have the role of Reporter.

I wasn't able to add the specific message in create_service.rb, but we test this for scenario in create_service_spec.rb.