[FIX] Duplicate User Reactions

[aditya-mitra]

Proposed changes (including videos or screenshots)

https://user-images.githubusercontent.com/55396651/104439142-ca37de80-55b6-11eb-980b-71e18c1c74da.mp4

Previously, if a user renamed himself and reacted again to the message, then his username would be added to the reaction again. This scenario has been fixed by considering the userIds array also into the reactions object.

https://user-images.githubusercontent.com/55396651/104439179-d6bc3700-55b6-11eb-8488-a8fdd33b9655.mp4

Also, when hovered over the reactions, You will be shown if the userId matches (and not the username).

Corner case situation ( where user2 has renamed himself to user1 and reacts to the message. Mentioned in detail in #20175 ) is also handled by creating a new array of usernames if the user's username is already there in the reactions object.

Issue(s)

Closes #6985 Closes #20175

Steps to test or reproduce

Further comments

I have also added a migration file (v213) for adding userIds array into the reactions object.

[aditya-mitra]

@dougfabris Please review :D

[aditya-mitra]

Should I update the migration file? (From v214 to v219)

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[Kunalvrm555]

hey @aditya-mitra this looks like a great fix but could you figure out why the checks failed. Please let me know