Accounts updated subscription

[Victor-N-Suadicani]

Purpose

I'm honestly not sure where this is used in the frontend.

Changes

Added the AccountsUpdatedSubscriptionItem and the appropriate methods to Subscription, which are largely inspired by the already-existing block_added subscription.

What's missing is actually sending the notifications when the appropriate event happens - this is left for future work.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

[DOBEN]

The AccountsUpdatedSubscription is used as part of the web socket connection when the accounts page view is open e.g.
https://testnet.ccdscan.io/?dcount=1&dentity=account&daddress=4dT5vPrnnpwVrXZgmYLtHrDLvBYhtzheaK4fDWbJewqRCGQKWz

You can open the network tab and click on the ws tab to explore the web socket connections in the DevTools in the browser.

[DOBEN]

Remaining logic to be added:

Whenever a new row is added to the affected_accounts table emit a trigger account_updated_notify_trigger_function() returning the account_affected as the address field in the notification type (similar to block_added_notify_trigger_function()).

https://github.com/Concordium/concordium-scan/blob/main/backend-rust/migrations/0001_initialize.up.sql#L376

Update: this is implemented now.

[DOBEN]

How to test:

• Open http://localhost:8000/ in browser
• Add subscription:

subscription accountsUpdatedSubscription($accountAddress: String) {
  accountsUpdated(accountAddress: $accountAddress) {
    address
  }
}

• Add variable (optional): e.g.

{
  "accountAddress": "4Y1c27ZRpRut9av69n3i1uhfeDp4XGuvsm9fkEjFvgpoxXWxQB"
}

• Press Play button:
• Observe Subscriptions coming in on the right side.

[soerenbf]

Still need to test it, but here are some initial observations

[soerenbf]

Managed to subscribe and receive an update 🎉