feat: Backend for Policy upload and store

[kairoaraujo]

Integration during the Policy upload and store in SQL and ObjectStorage

What this PR does / why we need it

Description

Which issue(s) this PR fixes (optional)

fixes #235

Acceptance Criteria Met

• Docs changes if needed
• Testing changes if needed
• All workflow checks passing (automatically enforced)
• All review conversations resolved (automatically enforced)
• DCO Sign-off

Special notes for your reviewer:

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 78 lines in your changes are missing coverage. Please review.

Project coverage is 1.49%. Comparing base (a035c62) to head (0ab4698).
Report is 64 commits behind head on main.

Files	Patch %	Lines
internal/metadatastorage/sqlstore/store.go	0.00%	78 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #251       +/-   ##
==========================================
- Coverage   82.40%   1.49%   -80.91%     
==========================================
  Files          10     117      +107     
  Lines         358   28635    +28277     
==========================================
+ Hits          295     429      +134     
- Misses         43   28149    +28106     
- Partials       20      57       +37     

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[mikhailswift]

The changes here are looking good. Guessing this still needs to be worked into the main Store call?

[kairoaraujo]

The changes here are looking good. Guessing this still needs to be worked into the main Store call.

Not sure if I got it.
This implementation is minimal but enables the store to download the policy. ☺️

I also added an e2e with a Policy dsse envelope.

[jkjell]

This looks good to me as is. I had a bit of wild 🤠 idea I suggested for storePolicy.

I spent a bit of time thinking if we could consolidate any of the code between storePolicy and storeAttestation but, they're just different enough.

Great work Kairo! 🎉

[ChaosInTheCRD]

There's nothing to me here that jumps out. All makes sense and is minimal, clean and easy to follow 😄

[kairoaraujo]

@jkjell rebased and solved the conflicts.