Fleet and Agent 9.0.8 release notes

[karenzone]

Docs release manager: @nastasha-solomon
Tech Writer: @karenzone

Fleet and Agent release notes

• Elastic-agent PR: Changelog 9.0.8 elastic-agent#10309

  • Forwardport to main: [main](backport #10309) Changelog 9.0.8 elastic-agent#10361
  • Forwardport to 9.1: [9.1] (backport #10309) Changelog 9.0.8 elastic-agent#10363

• Fleet-server PR: Changelog for 9.0.8 fleet-server#5626

  • Forwardport to main: [main](backport #5626) Changelog for 9.0.8 fleet-server#5630
  • Forwardport to 9.1: [9.1](backport #5626) Changelog for 9.0.8 fleet-server#5631

• Add PR links to docs release issue: [Docs release] 9.0.8

Forwardports 🎗️

• Verify that release notes PRs are forwardported to appropriate branches.
  Release notes are published from main, and are not live until the forwardport to main is complete. ❗