* MM-15021: Adding new builtin system schema for Guests
* Fixing tests
* Setting properly the permissions
* Adding guests to sampledata
* Restrict more roles updates in the app layer for guests
* Adding comment to explain that permissions migration must go at the end
* Setting the default guest role for custom scheme during migration
* Fixing import and export
* Creating scheme guest roles on migration
* Fixing tests
* Fixing tests
* Fixing tests
* MM-11424 Extend bulk import to support themes across teams(#9305)
Also added:
Advanced Settings:
+'feature_enabled_markdown_preview'
+'formatting'
Sidebar Settings:
+'show_unread_section'
* MM-11424 (PR review) user teams' theme validator test updated
* MM-11424 (PR review) added test with valid JSON of invalid theme(by structure)
JSON string contains numeric and JSON object fields, not just a correct "string":"string" map