Uncommitted migration work at the time of branch cleanup. Tagged as
checkpoint/m1-migration-wip so the commit survives git gc --prune=now.
Session context: Phase 3 Part B+C of the M-1 sentinel error migration
was in progress. 38 modified files, 4 new files (errors.go + errors_test.go
in internal/service/ and internal/api/handler/). Resume from this commit
via 'git checkout checkpoint/m1-migration-wip'.
Implements Simple Certificate Enrollment Protocol with single-endpoint
operation-based dispatch (GetCACaps, GetCACert, PKIOperation), PKCS#7
SignedData CSR extraction with fallback for raw/base64 CSR, challenge
password authentication via CSR attributes, and shared internal/pkcs7
package extracted from EST handler to eliminate code duplication.
24 new tests (11 service + 13 handler) plus 5 shared pkcs7 package tests.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
shankar0123