[jdk25] RFR: 8358099: PEM spec updates

Mon Jun 23 17:48:46 UTC 2025

Hi

This is a clean backport to jdk25 for updates to the PEM spec.

 PEMRecord.pem is renamed to content to better describe that it is the base64 content and not including the header and footer. Additionally, PEMRecord.getEncoded() is removed and some javadoc clarifications for PEMEncoder and PEMDecoder. 
Thanks.

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Commit messages:
 - Backport 78158f30aee51e14ab203b0127aeb883c010319c

Changes: https://git.openjdk.org/jdk/pull/25940/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25940&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8358099
  Stats: 68 lines in 6 files changed: 1 ins; 20 del; 47 mod
  Patch: https://git.openjdk.org/jdk/pull/25940.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25940/head:pull/25940

PR: https://git.openjdk.org/jdk/pull/25940