Summary

• Refactors OAuth flow detection to prioritize account-level AuthenticationType over destination definition config
• Moves OAuth detection in router from setup-time to per-batch processing, allowing different accounts for the same destination type to use different auth flows
• Propagates account information (DeleteAccount/DeliveryAccount) through regulation-worker and router transformer paths

Problem

Currently, we rely on the destination definition to determine whether to use OAuth flow. However, for destinations using accounts, we should use the account definition since a destination can support both non-OAuth and OAuth accounts (e.g., basic auth vs OAuth).

Solution

Updated IsOAuthDestination to:

1. First check if Account.AccountDefinition.AuthenticationType == "oauth"
2. Fall back to existing definitionConfig auth type check only if account info is unavailable

This ensures proper OAuth flow selection based on the actual account configuration rather than the destination's general capabilities.

Linear Ticket

https://linear.app/rudderstack/issue/INT-5712/fix-oauth-detection-logic-in-rudder-server

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.