Provide a native way to generate the ID from the sequence

[mipo256]

For now, there is no in-built way of generating the id from the sequence. The as mentioned here by @schauder, there is a way to achieve this via callbacks (one of the examples I believe can be found here)

That is a bit tedious, especially if we have multiple different entities in our persistence context (which is insanely often the case). We need to provide the utilities for ID generation from sequence on the framework side.

Related #842

[mipo256]

Hey @schauder!
Based on the discussion in this PR: #1922, can we rewrite the implementation in there via callbacks?

[schauder]

That is basically the expectation.