PR CIGate.ps1 support for Dependency scanning alerts (and a severity based policy)

[felickz]

This pull request includes significant changes to the src/pr-gating/CIGate.ps1 script, which is used for PR gating strategy. The changes enhance the script's functionality by improving alert handling and logging, and by modifying the script's variables and methods for better clarity and efficiency.

Key changes include:

• Refactored auth section (handle PAT that already contains :)
• Added new variables like $alertTypes, $severityPolicy to handle different types of alerts to create a policy
• Remove filter on alert types so that both code and dependency alerts are returned
• Updated the AddPRComment function to handle both dependency and code alerts. The function now checks the severity of the alert against a predefined policy before logging and reporting the alert. [1] [2] [3]
• Enhanced logging to provide more detailed information about the alerts. The script now logs the type, severity, and other details of the alert, and provides a link to the alert details in the Advanced Security UI.

These changes improve the script's ability to handle and report alerts, making it easier for developers to identify and fix potential issues in their code.

PR comment example:

[davidcatriel]

TODO: look into this here

27

The fix for handling empty target branch alerts (https://github.com/microsoft/GHAzDO-Resources/issues/27) worked well on my end. Consider changing line 172 from this:

# Check for alert ids that are reported in the PR source branch but not the pr target branch
$newAlertIds = Compare-Object $prSourceAlertIds $prTargetAlertIds -PassThru | Where-Object { $_.SideIndicator -eq '<=' }

To this:

# Fix for cases where the garget branch does not contain any alerts. Source: https://github.com/microsoft/GHAzDO-Resources/issues/27 
if ($null -eq $prTargetAlertIds) {
    $newAlertIds = $prSourceAlertIds 
} else {
# Check for alert ids that are reported in the PR source branch but not the pr target branch
    $newAlertIds = Compare-Object $prSourceAlertIds $prTargetAlertIds -PassThru | Where-Object { $_.SideIndicator -eq '<=' }
}