v4.21.0

✨ New content

• [Dev Docs] Clarify populate usage (#2034) @pwizla
• [Dev Docs] Add docs for keycloak users-permissions provider (#2048) @derrickmehaffy

🖌 Updated content

• [User Guide] Updates for stable release of Releases Scheduling (#2061) @pwizla

🧹 Chore, fixes, typos, and other improvements

• [Dev Docs] Add callout to lifecycle hooks to cross-link to error handling docs (#2058) @MbonuJennifer
• [Strapi Cloud] Cloud documentation backups updates (#2059) @meganelacheny

Thanks a lot for your contributions! 🥰🚀