NTV-277: Backer cannot comment on updates

[Arkariang]

📲 What

• Bring back the check around the current user being a backer

🤔 Why

• we recently added the field canComment to the project, it works perfectly for comments on a project. We did not had in mind though the comments on updates.

👀 See

commentsUpdates.mp4

Trello, screenshots, external resources?

Before 🐛	After 🦋

📋 QA

• Try to comment as a backer into a update from the project page
• Try to comment as a backer into a update from the activities page
• Check that you cannot comment on any update or project in which you are not backer

Story 📖

NTV-277

[codecov]

Codecov Report

Merging #1444 (649871a) into master (bca17c5) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1444   +/-   ##
=========================================
  Coverage     72.28%   72.28%           
  Complexity      736      736           
=========================================
  Files           210      210           
  Lines          6083     6083           
  Branches        391      391           
=========================================
  Hits           4397     4397           
  Misses         1548     1548           
  Partials        138      138           

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[hadia]

Tested👌
https://user-images.githubusercontent.com/1075310/140180602-24241127-b1dc-4aa1-a485-743eb0cd7f13.mp4