upgrade alpine base image from v3.20.3 to v3.21.0 including upgrade of borgbackup & openssh-server package (links below)
https://www.borgbackup.org/releases/borg-1.4.html
https://borgbackup.readthedocs.io/en/1.4-maint/changes.html#borg-1-2-x-to-1-4-x
https://git.alpinelinux.org/aports/commit/community/borgbackup?h=3.21-stable&id=1e1e3aeb81a3d2383cd945ed533c2d60ce34ed27
https://www.openssh.com/releasenotes.html
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=b34d5a41ca0caf54a746c676d3ea8103039e1687
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=e4bc62018e1fcd89bfa14970d0cd501502e816a5
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=bd8da62e7a2ec5f4d15a5b0f161c964cb670a5a7 (CVE-2024-6387)
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=3b45e188acbb29f3655ea041c3a8c88c34bf1eb8
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=db1426fd7e326c191ed43db416a2bdec5af98265
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=fd302541af01a709b81c42eb646ed5ded9fd0a7a
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=cdab729fb367ac85b56cde6017a09d736a603526
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=8a4e70bb2c6f5331e2e94b5c4be534713cd968c8
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.21-stable&id=6adff08ae09961d4eea66b55a8cca14d3941fb53