feat(flow): support passing a chain option

[roggervalf]

Imagine that you have 2 jobs (A and B), where B depends on the completion of A. This kind of dependency relationship should be handled by our waiting-children state.
What would happen if these 2 jobs happened in different transactions? In order have a way to link these 2 separated operations we need to track the reference of this chain of dependencies.
I'm introducing a new concept of saving a chain id reference where job A and B must provide it as option. Chain id and chain queueKey are used to build a chainKey to track the last jobKey reference to be used for the next subsequent jobs with same chain options to be added in the same dependency relationship.
Points to consider:

• ChainKey only saves the last job reference in the chain
• If last job in the chain finishes before a new job is added with same option, chain reference is deleted. New job will start a new chain.