UX design for errors that don't interrupt the user's workflow

This ticket is for creating the UX design when errors occur that don't interrupt the user's workflow.

Imagine you share a forum with someone or invite two contacts to each other. These operations might fail, but since the invitation screen closes anyway, it does not really interrupt your work-flow anymore. Another possible error might happen when a title of the blog or the number of online users is loaded to be shown in the action bar. There will just be the default title maybe "Blog" and the user might not even notice, but it is a bug we might want to know about. Another example is when we fail to store the fact that we already showed you the onboarding and then show it to you again.

So more general, the kinds of errors I imagine to fall in this category are:

user actions that are not completed, but don't interrupt the workflow because it finishes at this point anyway
loading of non-essential information

Subticket of #469.