fix: external transcript - handle mask identifiers [CHI-3874]

[gpaoloni]

Description

This PR addresses the issue mentioned in the linked ticket, where the trigger message (with contact identifier information) is displayed in external transcript, even if mask identifiers enabled.
This PR removes said message under above conditions, following the logic already present in the live chat.

Checklist

• Corresponding issue has been opened
• New tests added
• Feature flags added
• Strings are localized
• Tested for chat contacts
• Tested for call contacts

Verification steps

AFTER YOU MERGE

1. Cut a release tag using the Github workflow. Wait for it to complete and notify in the #aselo-deploys Slack channel.
2. Comment on the ticket with the release tag version AND any additional instructions required to configure an environment to test the changes.
3. Only then move the ticket into the QA column in JIRA

You are responsible for ensuring the above steps are completed. If you move a ticket into QA without advising what version to test, the QA team will assume the latest tag has the changes. If it does not, the following confusion is on you! :-P