Add resend OAuth2 provider to migration allow-list

[Meldiron]

What does this PR do?

Adds the new resend OAuth2 provider to the OAuth2Provider::PROVIDERS allow-list, following the same pattern as the recent appwrite (#207) and huggingface (#221) entries.

Appwrite server is adding a built-in Resend OAuth2 provider in appwrite/appwrite#13366. Its Migrations E2E suite currently fails because exporting a project surfaces:

{"code":500,"message":"No migration resource for OAuth2 provider 'resend'; skipped.","resourceName":"oauth2-provider","resourceGroup":"auth"}

Only clientId migrates (to the destination's resendAppid attribute). clientSecret is write-only and stays redacted per the existing allow-list policy — the destination side is fully generic, so no other changes are needed.

Test Plan

• Added testFromArrayResend to OAuth2ProviderTest, mirroring the existing per-provider tests.
• The existing testFromArrayNeverCopiesSecrets sweep now also covers resend and confirms clientSecret is never copied.
• ./vendor/bin/phpunit tests/Migration/Unit/Resources/OAuth2ProviderTest.php — 5 tests, 157 assertions, all passing; composer lint passes.

Related PRs and Issues

• Add Resend OAuth2 adapter appwrite/appwrite#13366 (failing Tests / E2E / PostgreSQL (dedicated) / Migrations check)

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

Adds the Resend OAuth2 provider to the migration allow-list while preserving the existing policy that excludes write-only client secrets.

• Maps Resend's clientId to the destination application-ID field.
• Adds focused normalization, destination-field, configuration, and secret-exclusion coverage.

Confidence Score: 5/5

The PR appears safe to merge with no actionable correctness or security issues identified.

The new provider follows the established allow-list mapping, reaches the destination’s generic provider-field handling, and retains the existing secret-exclusion boundary.

Important Files Changed

Filename	Overview
src/Migration/Resources/Auth/OAuth2/OAuth2Provider.php	Adds the resend provider using the existing generic client-ID mapping, which aligns with source parsing and destination attribute generation.
tests/Migration/Unit/Resources/OAuth2ProviderTest.php	Adds focused coverage confirming Resend normalization, application-ID mapping, configured state, and exclusion of the client secret.

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