Fix session cookie being recreated on every export

[rfontanarosa]

closes #1160

[codecov-commenter]

Codecov Report

❌ Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.29%. Comparing base (b62e49e) to head (9725ea7).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
web/src/app/services/auth/auth.service.ts	81.81%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2471      +/-   ##
==========================================
+ Coverage   60.07%   60.29%   +0.21%     
==========================================
  Files         115      115              
  Lines        2818     2826       +8     
  Branches      423      425       +2     
==========================================
+ Hits         1693     1704      +11     
+ Misses       1064     1061       -3     
  Partials       61       61              

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