feat(#96): add SecureSession to Serinus

[francescovallone]

Description

Add a Fastify secure session-like in serinus

Fixes #96

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

Attention: Patch coverage is 98.21429% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.94%. Comparing base (b51d450) to head (de6ec3b).
Report is 5 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ackages/serinus/lib/src/contexts/base_context.dart	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #103      +/-   ##
===========================================
+ Coverage    90.67%   90.94%   +0.26%     
===========================================
  Files           79       80       +1     
  Lines         2981     3025      +44     
===========================================
+ Hits          2703     2751      +48     
+ Misses         278      274       -4     

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