Refactor group member addition to use bulk requests

Replaces single PATCH request with bulk POST requests for adding group members. Improves error handling and logging by reporting failed additions and only listing successfully added users in the result message.

Author: JohnDuprey

Modules/CIPPCore/Public/Add-CIPPGroupMember.ps1

@@ -80,16 +80,29 @@ function Add-CIPPGroupMember {
                 }
             }
         } else {
-            $MemberIDs = foreach ($User in $Users) {
-                $ODataBindString -f $User.body.id
+            # Build one bulk request list; New-GraphBulkRequest handles internal chunking
+            $AddRequests = foreach ($User in $Users) {
+                @{
+                    id      = $User.body.id
+                    method  = 'POST'
+                    url     = "/groups/$($GroupId)/members/`$ref"
+                    body    = @{ '@odata.id' = ($ODataBindString -f $User.body.id) }
+                    headers = @{ 'Content-Type' = 'application/json' }
+                }
             }
-            $AddMembers = @{
-                '[email protected]' = @($MemberIDs)
+            $AddResults = New-GraphBulkRequest -tenantid $TenantFilter -Requests @($AddRequests)
+            $SuccessfulUsers = [system.collections.generic.list[string]]::new()
+            foreach ($Result in $AddResults) {
+                if ($Result.status -lt 200 -or $Result.status -gt 299) {
+                    $FailedUsername = $Users | Where-Object { $_.body.id -eq $Result.id } | Select-Object -ExpandProperty body | Select-Object -ExpandProperty userPrincipalName
+                    Write-LogMessage -headers $Headers -API $APIName -tenant $TenantFilter -message "Failed to add member $($FailedUsername): $($Result.body.error.message)" -Sev 'Error'
+                } else {
+                    $UserPrincipalName = $Users | Where-Object { $_.body.id -eq $Result.id } | Select-Object -ExpandProperty body | Select-Object -ExpandProperty userPrincipalName
+                    $SuccessfulUsers.Add($UserPrincipalName)
+                }
             }
-            $AddMemberBody = ConvertTo-Json -InputObject $AddMembers
-            $null = New-GraphPostRequest -uri "https://graph.microsoft.com/beta/groups/$($GroupId)" -tenantid $TenantFilter -type patch -body $AddMemberBody -Verbose
         }
-        $UserList = ($Users.body.userPrincipalName -join ', ')
+        $UserList = ($SuccessfulUsers -join ', ')
         $Results = "Successfully added user $UserList to $($GroupId)."
         Write-LogMessage -headers $Headers -API $APIName -tenant $TenantFilter -message $Results -Sev 'Info'
         return $Results