This PR fixes the indefinite hang issue (#819) by sanitizing SubjectCN and IssuerCN length and encoding. /claim #819

Summary by CodeRabbit

• Bug Fixes
  • Certificate issuer and subject common names are now sanitized: truncated to 256 characters and normalized to valid UTF-8 to prevent display or processing issues.
  • Responses now use the sanitized subject and issuer names and include those sanitized values in the response path.
  • Domain name handling and client-certificate error behavior remain unchanged.