Improve Related Issues error message when you don't have write permissions

With Related Issues, we should improve the error message when you don't have write permissions to the issue you are trying to relate.

Currently shows No Issue found for given params which doesn't describe the situation well.

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Opened because of this user report, https://gitlab.com/gitlab-org/gitlab-ee/issues/3069

mentioned in issue #3069 (closed)

@MadLittleMods imho the plus-button and the box it triggers should not be shown at all or replaced by a text similar to "You do not have the permission to manage related issues".

changed the description

@marco.schuster Thanks for the follow-up, there are two issues here.

I updated the issue to reflect the situation where you have access to manage the related issues but don't have write access to the issue you are trying to relate, currently it shows No Issue found for given params

The other issue is what you are mentioning is where the add button shouldn't show if you can't manage the related issues. It currently shows if you can update the issue. I have created a separate issue to follow, https://gitlab.com/gitlab-org/gitlab-ee/issues/3080

marked this issue as related to #3080 (closed)