Choose endpoints with tabs + QR code

[Janaka-Steph]

It closes #656

Trader endpoint tab has been disabled for now, just need to remove a line (see TODO).

Please review @tiero

[what-the-diff[bot]]

• Added a new tab for the trader endpoint
• Generated QR code from connect URL and added it to operator endpoint tab
• Changed some styles of tabs, messages etc...

[tiero]

LGTM