Add official support for Debian 11 with the latest ISPConfig release

Closes #57

See merge request ispconfig/ispconfig-autoinstaller!23

Merge branch '49-package-list-not-updated-after-adding-buster-backports-repo-on-debian-10' into 'master'

Resolve "Package list not updated after adding buster-backports repo on Debian 10"

Closes #49

See merge request ispconfig/ispconfig-autoinstaller!18

Resolve apt sources are not updated in debian (#43)

Closes #43

See merge request ispconfig/ispconfig-autoinstaller!16

Add buster-backports repo and install Roundcube from buster-backports on Debian 10 (#26)

Closes #26

See merge request ispconfig/ispconfig-autoinstaller!11

Install sudo and gnupg

See merge request ispconfig/ispconfig-autoinstaller!15

Jan Pechek authored Mar 23, 2021 and Marius Burkard committed Mar 23, 2021

Signed-off-by: Jan Pechek <honza@pechek.cz>

Resolve "Disable php8.0 on Apache2"

Closes #36

See merge request ispconfig/ispconfig-autoinstaller!13

Resolve "Add function to install certbot instead of acme.sh"

Closes #38

See merge request !14

Move hostname check to one of the first steps (#35)

Closes #35

See merge request !12