Enforce version limit in task queues

[ShahabT]

What changed?

Enforce a max limit on number of versions registered in a task queue.

Why?

Safety agains user data becoming too big.

How did you test it?

• [ ] built
• [ ] run locally and tested manually
• [ ] covered by existing tests
• [x] added new unit test(s)
• [ ] added new functional test(s)

Potential risks

User's polls will be rejected if server cannot allow new version registration due to the limit.