feat: include identity info in pseudo identity event payloads

[khushi1033]

Summary

Adds user_identities and user_attributes to individual identity event payloads (login, logout, modify_user, identify). Previously these fields were intentionally omitted from individual events since they exist on mparticle_batch in the metadata envelope. The requirement has changed and events need to carry this context individually for how they are consumed downstream.

Both fields are placed inside event.data (event-specific payload), following the Gateway TransactionEvent contract. user_attributes is snapshotted at callback time via the existing handleIdentityComplete ordering, so each event reflects the user state at the moment of the identity transition. user_identities has the emailsha256 key remapping applied before being set on the event.

Testing Plan

What has been tested

212/212 unit tests passing. Updated existing tests to assert data.user_identities and data.user_attributes. New tests added covering:

• Populated identities on login
• emailsha256 key remapping
• Populated user attributes on login
• Per-event attribute snapshot across multiple sequential callbacks
• Empty identities and attributes on anonymous logout

Screenshots

Before

After