mysql:5.7-debian image has dead apt config

[hcooper]

Debian buster is EOL so the database and backup_manager docker images can't build from scratch...

root@ubuntu-s-1vcpu-2gb-sfo3-01:~# docker run -it mysql:5.7-debian apt update
Ign:1 http://deb.debian.org/debian buster InRelease
Get:2 http://repo.mysql.com/apt/debian buster InRelease [22.1 kB]
Ign:3 http://deb.debian.org/debian-security buster/updates InRelease
Ign:4 http://deb.debian.org/debian buster-updates InRelease
Err:5 http://deb.debian.org/debian buster Release
  404  Not Found [IP: 151.101.202.132 80]
Err:6 http://deb.debian.org/debian-security buster/updates Release
  404  Not Found [IP: 151.101.202.132 80]
Err:7 http://deb.debian.org/debian buster-updates Release
  404  Not Found [IP: 151.101.202.132 80]
Err:2 http://repo.mysql.com/apt/debian buster InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B7B3B788A8D3785C
Reading package lists... Done
E: The repository 'http://deb.debian.org/debian buster Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://deb.debian.org/debian-security buster/updates Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://deb.debian.org/debian buster-updates Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://repo.mysql.com/apt/debian buster InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B7B3B788A8D3785C
E: The repository 'http://repo.mysql.com/apt/debian buster InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

[hcooper]

#169