Rethink persistence of system drives

[pschild]

Because there are issues with path.join(<DRIVELETTER>) and in order to make it work on different OSs, system drives should be persisted differently.

Using drivelist package, the information about the system drives can be the following (see https://github.com/balena-io-modules/drivelist):

# MacOS
mountpoints: [
    { "path": "/" },
    { "path": "/private/var/vm" }
]

# GNU/Linux
mountpoints: [
    { "path": "/" },
    { "path": "/boot/efi" }
]

# Windows
mountpoints: [
    { "path": "D:\\" }
]

Possibility A: Make it an own entity / save in own table

Possibility B: Add attribute isSystemDrive: boolean in Folder entity

Related: #10

[pschild]

Important properties of drivelist output:

isSystem: boolean: should be filtered by true (or do we need to take USB-Drives/SD-Cards into account? Is it also true for an HDD without OS?)
mountpoints: any[]: contains a list of the drive names
device: string/raw: string: contains the drive's name (may be important if mountpoints is an empty array)

[pschild]

Example output, including only important properties:

Windows (with USB-Drive):

[
  {
    "description": "SM951 NVMe SAMSUNG 512GB",
    "mountpoints": [
      {
        "path": "C:\\"
      }
    ],
    "isSystem": true,
    "isRemovable": false,
    "isCard": false,
    "isSCSI": true,
    "isUSB": false
  },
  {
    "description": "Intenso Ultra Line USB Device",
    "mountpoints": [
      {
        "path": "D:\\"
      }
    ],
    "isSystem": false,
    "isRemovable": true,
    "isCard": false,
    "isSCSI": false,
    "isUSB": true
  }
]

Linux (RPi with USB-Drive):

[
  {
    "description": "INTENSO Intenso Ultra Line",
    "mountpoints": [
      {
        "path": "/media/pi/INTENSO",
        "label": "INTENSO"
      }
    ],
    "isSystem": false,
    "isRemovable": true,
    "isCard": null,
    "isSCSI": false,
    "isUSB": true
  },
  {
    "description": "(boot, rootfs)",
    "mountpoints": [
      {
        "path": "/boot",
        "label": "boot"
      },
      {
        "path": "/",
        "label": "rootfs"
      }
    ],
    "isSystem": false,
    "isRemovable": true,
    "isCard": null,
    "isSCSI": null,
    "isUSB": null
  }
]