feat(adduser): add adduser plugin (#10441)

Automatic "Oh My ZSH" installation when adding new users

plugins/adduser/README.md

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+# adduser
+
+This plugin adds support for installing "Oh My ZSH" when adding new users.
+
+To use it, add `adduser` to the plugins array of your `~/.zshrc` file:
+
+```zsh
+plugins=(... adduser)
+```
+
+## Usage
+
+Just run `adduser` as you normally would do and now:
+
+1. The regular `adduser` command will run.
+2. The shell of the new user will switch to zsh
+3. "Oh My zsh will be installed (as if he would have ran `install.sh` himself).
+
+## NOTES
+
+- It is assumed that the last argument will be the username.<br>*(In rare cases people provide the group as last argument)*
+- `useradd` behaviour is not changed.
+
+## Author
+
+[Nikolas Garofil](https://github.com/ngaro)

plugins/adduser/adduser.plugin.zsh

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+# Copyright (c) 2021 Nikolas Garofil
+
+adduser() {
+	local returncode
+	local result_string="Installation of 'Oh My Zsh' "
+	local temp_installscript
+	local path_installscript="$ZSH/tools/install.sh"
+
+
+	#Create user, errors will be reported by the 'real' adduser
+	#Use which/tail combination to call the binary instead of this function
+	$(which -a adduser | tail -1) $@ || return 1
+
+
+	echo "\nUser '${@[$#]}' has been created. I will now try to install 'Oh My Zsh'"
+	if [[ -f $path_installscript ]] ; then
+
+		#copy install.sh to a new file in temp that we can give the right owner to execute
+		#and also make sure that after the install script we are no longer the new user
+		temp_installscript=$(mktemp)
+		cat $path_installscript | \
+		sed 's/exec zsh -l//' |
+	        sed 's/read -r opt/opt=y; echo "\n--- This time I am answering \\"yes\\" for you, but you will still have to type in the password of that user ---"/' \
+		> $temp_installscript
+		chown ${@[$#]} $temp_installscript && chmod +x $temp_installscript
+
+		#try installing with sudo or su when not available
+		if [[ -x $(which sudo) ]] ; then
+			sudo -u ${@[$#]} $temp_installscript
+			returncode=$?
+		else
+			if [[ -x $(which su) ]] ; then
+				su -l ${@[$#]} -c $temp_installscript
+				returncode=$?
+			else
+				echo "You can't become ${@[$#]} (no 'sudo' or 'su' available)" > /dev/stderr;
+				returncode=1
+			fi
+		fi
+		#cleanup
+		rm $temp_installscript
+	else
+		echo "Installationscript '$path_installscript' not available" 2> /dev/stderr;
+		returncode=1
+	fi
+
+	#mention the result
+	if [[ $returncode -eq 0 ]]; then
+		echo "$result_string succeeded."
+	else
+		echo "$result_string failed." 2> /dev/stderr
+	fi
+
+	return $returncode
+}