fix: Imported messages are not displayed

[matheusbsilva137]

Proposed changes (including videos or screenshots)

• Fix issue with imported messages not being displayed in the room.
• Fix importer agent being added as a member of every imported room.

Issue(s)

Ported from #29416

Steps to test or reproduce

Further comments

Imported messages were added along with a u._id field, which caused them not to be displayed (messages would have a u._id field and ALSO the uobject with the _id and username fields).

TC-732

[changeset-bot]

🦋 Changeset detected

Latest commit: dc8c2cf

The changes in this PR will be included in the next version bump.

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[codecov]

Codecov Report

Merging #29485 (dc8c2cf) into release-6.2.4 (82273fa) will increase coverage by 1.25%.
The diff coverage is n/a.

@@                Coverage Diff                @@
##           release-6.2.4   #29485      +/-   ##
=================================================
+ Coverage          45.64%   46.90%   +1.25%     
=================================================
  Files                722      729       +7     
  Lines              13713    13880     +167     
  Branches            2192     2197       +5     
=================================================
+ Hits                6259     6510     +251     
+ Misses              7153     7054      -99     
- Partials             301      316      +15     

Flag	Coverage Δ
e2e	46.87% <ø> (+1.25%)	⬆️

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