[backend] add referer policy (#16020)

[aHenryJard]

Proposed changes

• Set referer header to the minimal secure version.

See https://developer.mozilla.org/en-US/docs/Web/Security/Practical_implementation_guides/Referrer_policy

Related issues

• closes Update the referer request header to be more restricted #16020

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case (coverage and e2e)
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 34.88%. Comparing base (37fdf25) to head (9b820a4).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #16056   +/-   ##
=======================================
  Coverage   34.88%   34.88%           
=======================================
  Files        3211     3211           
  Lines      219359   219359           
  Branches    40715    40717    +2     
=======================================
+ Hits        76514    76517    +3     
+ Misses     142845   142842    -3     

Flag	Coverage Δ
opencti-client-python	46.36% <ø> (ø)
opencti-front	3.45% <ø> (ø)
opencti-graphql	71.80% <100.00%> (+<0.01%)	⬆️

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