Network Tab: Implement Network Overview

[diva-exchange]

The "Network" tab within the application is intended to display the dimensions of the DIVA network.

Wanted features

• Display the network, also as visible here: https://testnet.diva.exchange/ui/network
• Try to show the "activity" of the network participants. Examples: online or not, seen the last time, how often like when they have been online the last time, how active they are
• Keep in mind: activity stats can only be gathered as long as the local node is online.

What's needed

• REST API communication to the local blockchain instance (divachain), by default running on http://127.19.72.21:17468/ (API doc, here: https://github.com/diva-exchange/divachain). Example to load network list: http://127.19.72.21:17468/network
• SQLite database skills to store activity data as measured