All Configs which includes secrets to be passed through JobSpec & Assets during Dependency Resolution

[sravankorumilli]

TASK_BQ2BQ is the secret that is expected in bq2bq transformers which is a loosely coupled convention b/w server & client.
Rather every plugin should expect few configurations which include secrets and they all should be defined in the jobspec. Optimus just passes these details

Acceptance Criteria:

1. Update the contract to pass all the needed secrets through apis.
2. Update the bq2bq plugin