In order to share a link with others,

• I should see a "Share" Button on Report (non-editing) pages
• When I click the button, a modal should open containing an input field with the url to the current page so I can copy it

At a later stage, we should look into whether it is possible to display a button that directly copies the url to the clipboard.
The modal and its content should be identical to the wireframe in #OPT-755 (referring to the current Report instead of Dashboard in the heading of course).