Exception handling check and refactor

[maddyjoe]

As a young person I want to know when an exception error has happened and be told in a friendly-age appropriate way what has gone wrong

This is part 1 which covers assessing our current architecture and ensure handling = sensible (API) OR if any refactoring is needed

• currently business logic/operations are separate from the controller and model - this is good as we want it to support separate unit testing
• however we need to check our work, esp for e.g. scenarios where multiple operations take place in sequence within a call to perform a specific function --> to ensure that we are able to exception handle

On team discussion likely this is a good one for Steve/Lois to pair on.