Add entering the candidate id to the onboarding process

Why is this change being made?

This field was added to BambooHR so the data team can correctly link a Greenhouse candidate with a BambooHR employee. We need this because otherwise the Greenhouse reporting is not done 100% correctly.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what