Users should be able to purchase a subscription. This happens in the subscriptions page. They can't purchase a subscription if they don't have sufficient balance. This means, we should display the wallet information in the subscription page.
Since we are in the testnet phase, we should add a button to the wallet details section to receive free tokens. Said button should navigate users to our Telegram bot. Once users joined our channel, we send them testnet tokens.

The subscription page should show the updated balanced value. This means we have to listen to the events from the Blockchain (of course, through Streamer) to update the balance info (this is handled in #204).

We should also make sure the purchase buttons are disabled if the balance is not sufficient. If the balance if not sufficient for a subscription plan, we should inform the user with a message under the button.