Add a page after gateway was connected with success, asking to backup…

[Pierre-Gilles]

… the backup key

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• If your changes affects code, did your write the tests?
• Are tests passing? (npm test on both front/server)
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Description of change

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[codecov]

Codecov Report

Merging #740 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #740   +/-   ##
=======================================
  Coverage   92.24%   92.24%           
=======================================
  Files         419      419           
  Lines        5415     5415           
=======================================
  Hits         4995     4995           
  Misses        420      420           

Flag	Coverage Δ
#server	92.24% <ø> (ø)

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