Data retention: optionally preserve pinned posts

[cwarnermm]

@claude - Let's update the Mattermost Product Documentation to reflect the admin's data retention product experience from Mattermost server v10.10 onward in mattermost/mattermost#31165. Ensure the docs PR is added to the v10.10-documentation branch, not master. The doc updates include 2 parts: a server-side configuration setting that controls whether data retention should delete pinned posts or not, and an update to the data retention docs that pinned posts can be retained.

[claude]

Claude finished @cwarnermm's task —— View job • claude/issue-8070-20250618_123949 • [Create PR ➔](https://github.com/mattermost/docs/compare/master...claude/issue-8070-20250618_123949?quick_pull=1&title=Issue%20%238070%3A%20Changes%20from%20Claude&body=This%20PR%20addresses%20issue%20%238070%0A%0AGenerated%20with%20%5BClaude%20Code%5D(https%3A%2F%2Fclaude.ai%2Fcode)

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Documentation Updated Successfully! ✅

I've successfully updated the Mattermost Product Documentation to support the new data retention feature that optionally preserves pinned posts, available from Mattermost server v10.10 onward.

Changes Made

Configuration Documentation (source/configure/compliance-configuration-settings.rst):

• Added new Preserve pinned posts configuration setting
• Config path: .DataRetentionSettings.PreservePinnedPosts
• Environment variable: MM_DATARETENTIONSETTINGS_PRESERVEPINNEDPOSTS
• Default: false (pinned posts are deleted according to retention policy)
• When true: Pinned posts are preserved and not deleted by data retention policies

User Guide (source/comply/data-retention-policy.rst):

• Updated global retention policy setup instructions
• Added step for enabling pinned post preservation
• Updated FAQ section to clarify pinned post behavior
• Added note about availability from v10.10

Next Steps

Create a PR targeting the v10.10-documentation branch as requested.

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