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

Automatic "Oh My ZSH" installation when adding new users

plugins/adduser/adduser.plugin.zsh

@@ -0,0 +1,55 @@
+# 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
+}