The Blueprint struct is complex, deep, and full of references. This
means that any changes to it in memory will persist. Sometimes you need
an actual copy of it, so this adds DeepCopy which uses the json.Marshal
and Unmarshal functions to create a deep copy with no references to the
original.
This is not very efficient, but the alternative is adding Copy functions
to all the member structs and then calling them to build the copy.
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