Fix for #860 to avoid infinite loop

[merill]

Fix infinite loop during Graph API paging (#860)

When paging through large Graph API result sets (e.g., UserRegistrationDetails), if the API returns an error response that still contains @odata.nextLink, the export loop runs indefinitely. This also applies when transient 400 errors (like expired skip tokens) are immediately classified as non-retryable, causing the export to fail without retry.

Changes

4 files changed across 3 areas:

1. Paging loop hardening — Export-ZtGraphEntity.ps1

• Clear stale results: Set $results = $null at the start of each iteration so a failed API call (that was already retried five times) can't silently reuse the previous page's @odata.nextLink
• Try-catch around API call: Catches errors from Invoke-ZtRetry, logs the entity name/page/URI, then re-throws so the export is marked as Failed
• Error-response validation: Detects when Invoke-MgGraphRequest returns error JSON as a valid hashtable (with an error key) without throwing, and terminates the loop
• Stuck-paging detection: Tracks $previousNextLink and breaks if the same @odata.nextLink is returned on consecutive pages

2. Broader retry classification — Test-ZtRetryableError.ps1

• Changed from an allowlist (408, 429, 500, 502, 503, 504, 507) to a **denylist

[Copilot]

Pull request overview

Improves resiliency and diagnostics around Microsoft Graph exports by adding explicit error handling/validation and paging-loop safety checks, plus enhancing HTTP status code extraction for retry logic.

Changes:

• Add try/catch logging and detection of Graph “error” JSON responses during export paging.
• Add “stuck nextLink” detection to prevent infinite paging loops.
• Extend Get-ZtHttpStatusCode to parse raw HTTP status lines from exception messages.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/powershell/private/export/Export-ZtGraphEntity.ps1	Adds error logging/validation around Graph responses and adds stuck-paging detection during export.
src/powershell/private/core/Get-ZtHttpStatusCode.ps1	Adds an additional regex strategy to extract 4xx/5xx codes from raw HTTP status lines in exception messages.

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[Copilot]

Pull request overview

Improves the robustness of Microsoft Graph exports and retry handling by adding better error detection/logging in paging exports, broadening retry behavior, and enhancing HTTP status code extraction to recognize more error message formats.

Changes:

• Add structured logging and error-response detection to Export-ZtGraphEntity, plus stuck paging detection.
• Change retry policy to treat most HTTP status codes as retryable except 401/403/404.
• Extend HTTP status code extraction to parse raw HTTP/x.y <status> status lines and update retry tests accordingly.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
src/powershell/private/export/Export-ZtGraphEntity.ps1	Adds logging, error-response validation, and stuck nextLink detection during paged exports.
src/powershell/private/core/Test-ZtRetryableError.ps1	Changes retryability logic to a denylist (only 401/403/404 are non-retryable).
src/powershell/private/core/Get-ZtHttpStatusCode.ps1	Adds regex strategy to extract status codes from raw HTTP status lines.
code-tests/commands/Invoke-ZtRetry.Tests.ps1	Updates test expectation to retry HTTP 400 errors.

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[alexandair]

@merill Please, address my feedback.