rework code to enable/disable remote support

we had a generic ssh key management api. this was causing issues because
the ssh format is more complicated than what we had implemented. currently,
the only use case we have is to add our ssh key.

Fixes #600

src/scripts/remotesupport.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+
+set -eu -o pipefail
+
+if [[ ${EUID} -ne 0 ]]; then
+    echo "This script should be run as root." > /dev/stderr
+    exit 1
+fi
+
+if [[ $# -eq 0 ]]; then
+    echo "No arguments supplied"
+    exit 1
+fi
+
+if [[ "$1" == "--check" ]]; then
+    echo "OK"
+    exit 0
+fi
+
+CLOUDRON_SUPPORT_PUBLIC_KEY='ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDQVilclYAIu+ioDp/sgzzFz6YU0hPcRYY7ze/LiF/lC7uQqK062O54BFXTvQ3ehtFZCx3bNckjlT2e6gB8Qq07OM66De4/S/g+HJW4TReY2ppSPMVNag0TNGxDzVH8pPHOysAm33LqT2b6L/wEXwC6zWFXhOhHjcMqXvi8Ejaj20H1HVVcf/j8qs5Thkp9nAaFTgQTPu8pgwD8wDeYX1hc9d0PYGesTADvo6HF4hLEoEnefLw7PaStEbzk2fD3j7/g5r5HcgQQXBe74xYZ/1gWOX2pFNuRYOBSEIrNfJEjFJsqk3NR1+ZoMGK7j+AZBR4k0xbrmncQLcQzl6MMDzkp support@cloudron.io'
+
+cmd="$1"
+keys_file="$2"
+user="${3:-1000}"
+
+if [[ "$1" == "is-enabled" ]]; then
+    if grep -q "${CLOUDRON_SUPPORT_PUBLIC_KEY}" "${keys_file}"; then
+        echo "true"
+    else
+        echo "false"
+    fi
+elif [[ "$1" == "enable" ]]; then
+    mkdir -p $(dirname "${keys_file}")       # .ssh does not exist sometimes
+    touch "${keys_file}"                # required for concat to work
+    if ! grep -q "${CLOUDRON_SUPPORT_PUBLIC_KEY}" "${keys_file}"; then
+        echo -e "\n${CLOUDRON_SUPPORT_PUBLIC_KEY}" >> "${keys_file}"
+        chmod 600 "${keys_file}"
+        chown "${user}" "${keys_file}"
+    fi
+elif [[ "$1" == "disable" ]]; then
+    if [[ -f "${keys_file}" ]]; then
+        sed -e "/ support@cloudron.io$/d" -i "${keys_file}"
+    fi
+fi
+