add simple left navigation
refactor sheet tabs to declarative form in order to keep active tab when switching groups
clean up unused code
fix style according to rubocop
preload hierarchy for left nav groups
improve style according to rubocop
increase db pool
update gems
fix more rubocop violations
reduce paddings in tables
fix bug in mover, try to order groups alphabetically on create
order groups alphabetically
show trace if tx:pull fails in rpm build
only move nodes if anything changes
also update layer group id after update
add default locale for mailers
show participation for all courses, reset event_id in participant_assigner#remove_role, fixes #6812
track name change to trigger move
refactor group class, add tests
update rails version