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To assign healthCode to an ID is to assign it, but I propose a reservation design so that during sign up, we can validate and hold an ID until we have an account with a healthCode that we can register in the first place. The reservation would only be for 30 seconds or so.
ExternalIdDao
Follows the external ID service. The service might assume methods for FPHS and the FPHS Dao as well, not sure.
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