add mutex to sample addition update via api/v1/

[antgonza]

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[antgonza]

from @wasade: mutex should be pushed down into the objects not the interfaces. Otherwise a user could trigger a prep file recreation from the gui while in parallel a user could trigger one via the rest api

[antgonza]

@wasade, thinking more about this: the mutex is already implemented as part of the pgSQL transactions, so not sure if worth implemented at the object level as the only reason we do this in the GUI is so users avoid double clicking on the interface, which is pretty common ... thoughts?