add chat members to the backup

[ryanfkeepers]

lazily fetch the chat members and add them to the chat during backup item downloads.

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Does this PR need a docs update or release note?

• ⛔ No

Type of change

• 🌻 Feature

Issue(s)

• 1:1 chats v0 and v1 backup support #5063

Test Plan

• 💪 Manual
• ⚡ Unit test
• 💚 E2E

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[sonarcloud]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud