As requested by @s-ben, we map now include cred over time for all
contributions, not just contributors. Based on discussion with @Beanow,
we made it an optional field so that we can optionally filter to save
space instead.
I was initially concerned that we wouldn't be able to compute
credOverTime for non-user nodes in CredRank, which is why I left it out.
However, informed by discussions with @mZargham, I'm less concerned
because PageRank (and thus CredRank) is a linear operator on the seed
vector. So, if we want to compute the "cred over time" for individual
contributions in CredRank, we can do so by constructing time-specific
seed vectors (which flow only to activity minting cred in the specified
interval), and the sum of contributions time-scoped cred will be equal
to the non-time-scoped cred. It's good that we'll still have the epoch
nodes for users, as that will allow us to model sponsorship cred flow
dynamics.
cc @wchargin for CredRank considerations.
Test plan: Unit tests updated, `yarn test` passes.
91ca897d99