Add board visibility (private/shared/public) for multiuser mode#122

Copilot wants to merge 3 commits intolstein/feature/workflow-isolation-in-multiuser-modelstein/InvokeAI:lstein/feature/workflow-isolation-in-multiuser-modefrom

copilot/enhancement-allow-shared-boardslstein/InvokeAI:copilot/enhancement-allow-shared-boardsCopy head branch name to clipboard