[PMS] Workflow improvements

The current workflow only has 1 type of 'blocks' - the prompt block where data is processed by a prompt internally and fed direct to the next block. I'm proposing we add another block that gatekeeps the data passing through - essentially either making sure the data is the type we want. It should be something that can be handled by a smaller LLM, ideally like a 7B instance where simple classification or checking is done.