Improve error messages

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"Something has gone wrong" is not helpful to an end-user. In general we need to review error messages, maybe also other messages, to make sure they are useful in the eyes of an end-user and not a developer.

Escape option

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There should always be at least one escape option for a user. We should make sure the client is always known. This can be done by adding the client uuid to the client session code, which means it will be always be available even if session has been cleared. As long as the client has set the base url we can add a link to return the application. 

As the logins are redirect based it's important to always be able to return to the application, especially for consumer facing sites.

I'm not sure "back to application" is the best text though, but can't come up with anything better ATM.

There's also several times in the flow it could be useful to have a cancel/restart option to restart the flow. Again, I'm not sure what the best text for the link is. "cancel" would suggest returning to the application, not to restart the flow.

Back/refresh buttons

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Using cache control it should be possible to always reload the page so when a user clicks back the current page is just redisplayed.