upgrade alpine base image to v3.15.0 including upgrade of mariadb-client package to v10.6.4-r1 and openssh-server package (see below)
https://web.archive.org/web/20210812164815/https://mariadb.com/kb/en/mariadb-1060-release-notes/
https://web.archive.org/web/20210812061824/https://mariadb.com/kb/en/mariadb-1061-release-notes/
https://web.archive.org/web/20210630053351/https://mariadb.com/kb/en/mariadb-1062-release-notes/
https://web.archive.org/web/20210811184553/https://mariadb.com/kb/en/mariadb-1063-release-notes/
https://web.archive.org/web/20210813014309/https://mariadb.com/kb/en/mariadb-1064-release-notes/
https://git.alpinelinux.org/aports/commit/main/mariadb?h=3.15-stable&id=3d5fe2e6ddf7c935c9f6f358998e14506e146e1a
https://git.alpinelinux.org/aports/commit/main/mariadb?h=3.15-stable&id=ccd1dd9dedc58b979d09debe03cb3cebc390c202
https://git.alpinelinux.org/aports/commit/main/mariadb?h=3.15-stable&id=8a845902403a3d268da120ce5df43400e3f5654b
https://git.alpinelinux.org/aports/commit/main/mariadb?h=3.15-stable&id=5673699d73c47d426e7932093203809f78bda207
https://git.alpinelinux.org/aports/commit/main/mariadb?h=3.15-stable&id=f3d3b2d920bafb894bdc14abfcc3b381685c8615
https://web.archive.org/web/20211204063543/https://www.openssh.com/releasenotes.html
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.15-stable&id=8293eb79d181515827092ec15f9dcb24989959c6
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.15-stable&id=e05faf293fd802c729d432906ffb5e8db77f3830
https://git.alpinelinux.org/aports/commit/main/openssh?h=3.15-stable&id=b5e3d52e5a95ff8a73c23908201474bb15048a11