Add a way to easily wait for job completion

[dlee]

It would be nice to have a way to "join" a job like joining a Thread to wait for job completion.

[javierjulio]

I haven't really thought about that. If I had multiple jobs running that were unrelated I would just schedule to run them at different times (using whenever gem). Do you have some ideas as to how this could be done? I'm thinking if you are joining jobs that are dependent on when they finish that maybe we'd want a database layer to deal with failures (I bring this up as when I first read the request Delayed::Job came to mind). I haven't had a need for this so I'm not sure what would be best or more importantly if its necessary. What is your experience?