support nullable domain-value-object reference

[uladkasach]

right now, in the upsert function, it is trying to resolve the domain value object id without checking if the input for that property was null

typescript is catching this so no biggie, but its making the user have to fix it themselves

[uladkasach]

e.g., from

      searchTermId: googleAdsExposureTrigger.searchTerm.id
        ? googleAdsExposureTrigger.searchTerm.id
        : (
            await googleAdsSearchTermDao.upsert({
              dbConnection,
              googleAdsSearchTerm: googleAdsExposureTrigger.searchTerm,
            })
          ).id,

to

      searchTermId: googleAdsExposureTrigger.searchTerm
        ? googleAdsExposureTrigger.searchTerm.id
          ? googleAdsExposureTrigger.searchTerm.id
          : (
              await googleAdsSearchTermDao.upsert({
                dbConnection,
                googleAdsSearchTerm: googleAdsExposureTrigger.searchTerm,
              })
            ).id
        : null,