Deprecate XCMv3

[bkontur]

Now that we have XCMv5 released, we should deprecate XCMv3, similar to how we deprecated XCMv2 when we introduced XCMv4.

TODO

• Deprecate XCMv3
• Check, fix, or remove MIN_XCM_VERSION – see comment here
• Backport to all stable2412 and stable2503 versions (should be fine, as Fellows has migrated to xcm::v4 – reference

[xlc]

why backport to existing stable versions?

[bkchr]

Yeah and we should also not remove the code if not really needed.

[bkontur]

why backport to existing stable versions?

my mistake - not to all, but only to those containing XCMv5 (stable2412, stable2503). I think we should backport Deprecate XCMv3 so that downstream users upgrade in advance (kind of forcing them to migrate to XCMv4 or XCMv5).

@franciscoaguirre Do we have documentation somewhere on adding new XCM versions and the deprecation process? I think I saw it "somewhere"?

Yeah and we should also not remove the code if not really needed.

MIN_XCM_VERSION was introduced/merged just last week, and I believe it is not really needed to expose it from xcm module.

[xlc]

Is there a v4 / v5 migration guide? I have no idea where to look up for guides.

I tried search v5 on this page and there is no result? https://github.com/paritytech/polkadot-sdk/releases?page=1

[programskillforverification]

I would like to work on this. Please assign to me.