feat(installer): validate disk space before installation

[ppawlowski]

Description

This pull request adds a free disk space validation to the Device Agent Installer pre-install check.
As a result, Installer will verify if the installation and temporary directories have enough disk space to perform an installation.

To validate this solution:

On Windows

Fill up a C:\ disk drive by creating large file and leaving ~200M of free disk space.
Following command will create a 10G file on c: drive:

fsutil file createnew C:\largefile.dat 10737418240

Run the installer afterwards - it should fail if there is less than 512M of free disk space

Cleanup:

del C:\largefile.dat

On Linux

• create a 128MB file
• format file with ext4 filesystem
• mount file

truncate -s 128M /tmp/loopback.img
mkfs.ext4 /tmp/loopback.img
mkdir /mnt/smallfs
mount -o loop /tmp/loopback.img /mnt/smallfs

• use the installer to install the device agent into the mounted filesystem:

./flowfuse-device-agent-installer --otc come-code-here --dir /mnt/smallfs/flowfuse-agent

• Set TMPDIR to the mounted filesystem:

export TMPDIR=/mnt/smallfs

• run the installer again, without the --dir flag to validate TMP disk space validation.

/flowfuse-device-agent-installer --otc come-code-here 

Cleanup:

sudo umount /mnt/smallfs
rm /tmp/loopback.img
rm -rf /mnt/smallfs
unset TMPDIR

Related Issue(s)

Closes #494

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[Steve-Mcl]

@ppawlowski did you notice conflicts?

[ppawlowski]

@ppawlowski did you notice conflicts?

Fixed

[hardillb]

ERROR] Disk space check failed: insufficient disk space in install directory (/mnt/smallfs/dev): need at least 524288000 bytes, available 99553280 bytes

only niggle and not worth stopping shipping would be to convert bytes to megabytes as it's easier to read.

[ppawlowski]

@Steve-Mcl can you take a look at this PR, please?