Provide TLS 1.3 support for 3.5.

[ramses]

What would you like to be added?

TLS 1.3 support was (re-)added to the main branch in #15156

... thus resolving #13506

However, organizations running etcd 3.4 and 3.5 are starting to require TLS 1.3 for security compliance.

---

The "3.4 version" analogue issue: #15437

Why is this needed?

As stated above, organizations running etcd 3.4 and 3.5 are starting to require TLS 1.3 for security compliance. Also, waiting for etcd 3.6 is not compatible with their timelines.

[serathius]

LGTM
cc @ptabor @spzala @ahrtr

[ahrtr]

Makes sense to me. Please feel free to deliver a PR, thx

[jmhbnz]

Initial backport pr merged and docs pr open here etcd-io/website#650.

I will raise pr for 3.5.8 changelog shortly, quick question @ahrtr the change touches several aspects of the codebase, do you want just one section updated in the changelog, or under all impacted?

/assign
/remove help

[ahrtr]

I will raise pr for 3.5.8 changelog shortly, quick question @ahrtr the change touches several aspects of the codebase, do you want just one section updated in the changelog, or under all impacted?

NO strong opinion on this. Only adding changelog item for etcdserver seems OK to me. Please backport the PR to 3.4 as well if you have bandwitdh, and after changelog for both 3.5 and 3.4 afterwards. thx.