feat: archivistactl import

[kairoaraujo]

What this PR does / why we need it

Introduces a new archivistactl import

It allows Archivista users to import DSSE Envelopes directly to the Archivista database.

The feature allows direct import, which can help import huge amounts of data as it uses concurrency (go routines) to process.

Performance examples

Importing 2100 new DSSE Envelopes

Using default: --max-concurrent 3

Using --max-concurrent 10

Which issue(s) this PR fixes (optional)

(optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged)*

Related #319

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:

TODO:

• Unit Tests
• Sub-features (nice to have)
  • --exist-first fail in the first import error instead of skipping

I can add the TODO as new commits or as new PRs.

[codecov]

Codecov Report

Attention: Patch coverage is 7.00000% with 93 lines in your changes missing coverage. Please review.

Project coverage is 1.64%. Comparing base (a035c62) to head (f670f06).
Report is 152 commits behind head on main.

Files	Patch %	Lines
cmd/archivistactl/cmd/import.go	7.00%	93 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #358       +/-   ##
==========================================
- Coverage   82.40%   1.64%   -80.76%     
==========================================
  Files          10     121      +111     
  Lines         358   28956    +28598     
==========================================
+ Hits          295     477      +182     
- Misses         43   28422    +28379     
- Partials       20      57       +37     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.