Push Task to Ordered Set

[nsteinberg-r7]

Description:
enable pushing tasks to ordered sets, to ensure avoiding duplication in queue.
I see this is how the delayed tasks feature is implemented, it could be helpful to have it also as a normal push_task.

[wavenator]

Your implementation won't work, and it won't work by design.
The reason it won't work is that inside each task there is a date parameter of type float, which will make tasks with the same kwargs different in their serialized representation. The only way to avoid duplication is to not create them in the first place. We are not going to work with a Redis zset as it poses other issues that we are not willing to solve. Tasks will lose their order is a set which will be set according to the data hashed representation according to Redis implementation. Zset is also much slower than lists. I'm closing this PR for the aforementioned reasons. If you would like to open a discussion about this feature feel free to open an issue where we will think about the implications and the appropriate design.

Cheers