feat(server): send invitation notification

[fengmk2]

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[fengmk2]

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• feat(server): send invitation accepted notification #10421
• feat(server): send invitation review notification #10418
• feat(server): send invitation notification #10219 👈 (View in Graphite)
• feat(server): notification system #10053
• feat(server): add user existence check and public user fill methods #10402
• feat(server): add workspace avatar support in doc reader #10390
• canary

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@                        Coverage Diff                        @@
##             02-10-feat_server_notification   #10219   +/-   ##
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  Coverage                                  ?   48.83%           
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  Files                                     ?     2346           
  Lines                                     ?   109038           
  Branches                                  ?    17172           
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  Hits                                      ?    53250           
  Misses                                    ?    54456           
  Partials                                  ?     1332           

Flag	Coverage Δ
server-test	63.32% <100.00%> (?)
unittest	31.19% <ø> (?)

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