Update CHANGELOG.md for 12.8.0

[ci skip]

changelogs/unreleased/sh-update-acme-client.yml

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-title: Upgrade acme-client to v2.0.5
-merge_request: 23498
-author:
-type: other

changelogs/unreleased/sh-use-cte-for-projects-finder.yml

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-title: Use CTE optimization fence for loading projects in dashboard
-merge_request: 23754
-author:
-type: performance

changelogs/unreleased/show-kubernetes-namespace-on-job-show-page.yml

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-title: Show Kubernetes namespace on job show page
-merge_request: 20983
-author:
-type: added

changelogs/unreleased/show_selected_template_type.yml

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-title: Show selected template type when clicked
-merge_request: 24596
-author:
-type: fixed

changelogs/unreleased/ss-fix-text-truncated-on-board-list.yml

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-title: Add styles for board list labels when text is too long
-merge_request: 24627
-author:
-type: fixed

changelogs/unreleased/sy-sync-issues-with-sentry.yml

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-title: Sync GitLab issue back to Sentry when created in GitLab
-merge_request: 23007
-author:
-type: added

changelogs/unreleased/sy-sync-plugin-sentry-issues.yml

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-title: Sync GitLab issues with Sentry plugin integration
-merge_request: 23355
-author:
-type: added

changelogs/unreleased/tc-create-project-settings.yml

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-title: Introduce project_settings table
-merge_request: 19761
-author:
-type: added

changelogs/unreleased/tc-fix-38088.yml

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-title: Ensure a valid mount_point is used by the AvatarUploader
-merge_request: 24800
-author:
-type: fixed

changelogs/unreleased/tidy-cluster-advanced-settings.yml

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-title: Use consistent layout in cluster advanced settings
-merge_request: 22656
-author:
-type: other

changelogs/unreleased/toggle-analytics-navbar-feature-flags.yml

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-title: Move analytics pages under the sidebar for projects and groups
-merge_request: 24470
-author:
-type: changed

changelogs/unreleased/tr-fix-frontend-polling.yml

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-title: Ensure that error tracking frontend only polls when required
-merge_request: 23305
-author:
-type: fixed

changelogs/unreleased/turn-on-merged-branch-cache-flag.yml

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-title: Cache repository merged branch names by default
-merge_request: 24986
-author:
-type: performance

changelogs/unreleased/unauthaccess-to-public-keys.yml

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-title: Allow SSH keys API endpoint to be requested for a given username
-merge_request: 22899
-author: Rajendra Kadam
-type: changed

changelogs/unreleased/update-geo-node-service.yml

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-title: Use NodeUpdateService for updating Geo node
-merge_request: 23894
-author: Rajendra Kadam
-type: changed

changelogs/unreleased/update-gitlab-runner-helm-chart-to-0-13-0.yml

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-title: Update GitLab Runner Helm Chart to 0.13.0/12.7.0
-merge_request: 23308
-author:
-type: other

changelogs/unreleased/update-gitlab-runner-helm-chart-to-0-13-1.yml

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-title: Update GitLab Runner Helm Chart to 0.13.1 (GitLab Runner 12.7.1)
-merge_request: 23588
-author:
-type: other

changelogs/unreleased/update-graphicsmagick-to-1-3-34.yml

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-title: Update GraphicsMagick from 1.3.33 to 1.3.34
-merge_request: 24225
-author: Takuya Noguchi
-type: security

changelogs/unreleased/update-handlebarsjs.yml

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-title: Update handlebars to remove issues from dependency dashboard
-merge_request:
-author:
-type: security

changelogs/unreleased/update_cluster-applications_v0-7-0.yml

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-title: Updated cluster-applications to v0.7.0
-merge_request: 24754
-author:
-type: changed