Add changelog items

changelogs/unreleased/dm-add-sudo-scope.yml

+---
+title: Add sudo scope for OAuth and Personal Access Tokens to be used by admins to
+  impersonate other users on the API
+merge_request:
+author:
+type: added

changelogs/unreleased/dm-convert-private-tokens.yml

+---
+title: Convert private tokens to Personal Access Tokens with sudo scope
+merge_request:
+author:
+type: security

changelogs/unreleased/dm-remove-private-token-from-interface.yml

+---
+title: Remove private tokens from web interface and API
+merge_request:
+author:
+type: security

changelogs/unreleased/dm-remove-private-token.yml

+---
+title: Remove Session API now that private tokens are removed from user API endpoints
+merge_request:
+author:
+type: removed