fix: removes attestation payload from attest-blob's output & no base64 encoding

[asraa]

Fixes #2497

• fix!: This writes and prints the signature (DSSE envelope) output as the JSON, NOT base64-encoded. Previously, this would base64-encode the envelope
• fix!: This removes printing the attestation JSON to the std output. This confuses piping the output, since now both the DSSE envelope and the attestation are printed.
• fix!: verify-blob-attestation now expects a JSON DSSE envelope (NOT base64-encoded)

BREAKINGCHANGE

• verify-blob-attestation expects the JSON DSSE envelope. Previously, this was expected to be base64-encoded.
• attest-blob outputs only the JSON DSSE envelope. Previously, it also printed the intoto attestation payload and the DSSE envelope was additionally base64-encoded.

Signed-off-by: Asra Ali asraa@google.com

Summary

Release Note

Documentation

[codecov-commenter]

Codecov Report

Merging #2498 (8490832) into main (64e7719) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2498   +/-   ##
=======================================
  Coverage   30.01%   30.01%           
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  Files         139      139           
  Lines        8592     8592           
=======================================
  Hits         2579     2579           
  Misses       5655     5655           
  Partials      358      358           

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[priyawadhwa]

LGTM!