Generate secure byte array and encode it with base64 string.

GenerateApiKey.ps1

param(
    [int]$SecretArrayLength = 64
)

$randomNumberGenerator = [System.Security.Cryptography.RandomNumberGenerator]::Create();
$ba = [Byte[]] (,0 * $SecretArrayLength);

$randomNumberGenerator.GetBytes($ba, 0, $SecretArrayLength);

return [System.Convert]::ToBase64String($ba);