impl(storage): add SignedUrlBuilder

[alvarowolfx]

Adds just the SignedUrlBuilder without the actual signing logic, so we can focus on validating the public API.

Towards #3645

[codecov[bot]]

Codecov Report

:x: Patch coverage is 93.18182% with 3 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 95.22%. Comparing base (afd5659) to head (cad0241). :warning: Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
src/storage/src/error.rs	80.00%	2 Missing :warning:
src/storage/src/storage/signed_url.rs	97.05%	1 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3985   +/-   ##
=======================================
  Coverage   95.22%   95.22%           
=======================================
  Files         171      172    +1     
  Lines        6467     6511   +44     
=======================================
+ Hits         6158     6200   +42     
- Misses        309      311    +2     

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[coryan]

/cc: @BenWhitehead FYI...