internal/functions/resolve/Resolve-Group.ps1

function Resolve-Group
{
    [CmdletBinding()]
    Param (
        [Parameter(Mandatory = $true)]
        [string] $InputReference,
        [switch] $DontFailIfNotExisting,
        [switch] $SearchInDesiredConfiguration,
        [System.Management.Automation.PSCmdlet]
        $Cmdlet = $PSCmdlet
    )
    
    begin {
        $InputReference = Resolve-String -Text $InputReference
        $token = (Get-AzAccessToken -AsSecureString -ResourceUrl "https://graph.microsoft.com").Token
        Connect-MgGraph -AccessToken $token | Out-Null
        Test-GraphConnection
    }
    process
    {            
        try {
            if ($InputReference -match $script:guidRegex) {
                $group = (Invoke-MgGraphRequest -Method GET -Uri ("$script:graphBaseUrl/groups/{0}" -f $InputReference) -Headers @{"Authorization"= "Bearer $($token)"}).Id
            }
            elseif ($InputReference -match $script:mailNicknameRegex) {
                $group = (Invoke-MgGraphRequest -Method GET -Uri ("$script:graphBaseUrl/groups/?`$filter=mailNickname eq '{0}'" -f $InputReference) -Headers @{"Authorization"= "Bearer $($token)"}).Value.Id
            }
            elseif ($InputReference -in @("All")) {
                return $InputReference
            }
            else {
                $group = (Invoke-MgGraphRequest -Method GET -Uri ("$script:graphBaseUrl/groups/?`$filter=displayName eq '{0}'" -f $InputReference) -Headers @{"Authorization"= "Bearer $($token)"}).Value.Id
            }
            
            if (-Not $group -and $SearchInDesiredConfiguration) {
                if ($InputReference -in $script:desiredConfiguration["groups"].displayName) {
                    $group = $InputReference
                }
            }

            if (-Not $group -and -Not $DontFailIfNotExisting) { throw "Cannot find group $InputReference" } 
            elseif (-Not $group -and $DontFailIfNotExisting) { return }

            if ($group.count -gt 1) { throw "Got multiple groups for $InputReference" }
            return $group
        }
        catch {
            Write-PSFMessage -Level Warning -String 'AzurePIM.CannotResolveResource' -StringValues "Group" -Tag 'failed' -ErrorRecord $_
            $Cmdlet.ThrowTerminatingError($_)                
        }            
    }
}