Avoid recommending backwards-incompatible version bumps

[hseg]

(Cross-posting this from
CycloneDX/cyclonedx-python-lib#775 (comment),
since right after posting it I realized this might be more useful here)

In reading the migration advisory for v2.0.0, I'm struck that it makes
packages depending on serializable more brittle, as they'll only be compatible
with serializable ^>= 2.0.0. In particular, this means that on systems (in my
case, Arch Linux's AUR) packaging serializable and some of its reverse
dependencies, the entire set of packages needs to be updated in lockstep (of
course, some of that fragility is also due to Python not supporting multiple
installed versions of packages and Arch Linux's norms being averse to placing
upper bounds on dependencies).
This is particularly ironic given the context for this change was to make the
packaging situation better (avoiding naming conflicts).

Instead, it might make sense to reword the advisory so it recommends something
like

from importlib.metadata import version
from packaging.Version import Version

match Version(version('py-serializable')):
    case ver if ver < Version('2.0.0'):
        import serializable
    case ver if Version('2.0.0') <= ver < Version('3.0.0'):
        import py_serializable as serializable
    case _:
        throw ImportError("Can't predict py-serializable compatibility")

and similarly for the other changes.

[jkowalleck]

the breaking change from v1 to v2 was intentional. that was the whole reason for the new major version release.