[Specs] Push Subscribe, Push Update and Notification Types

[pedrouid]

This new protocol will essentially allow Dapp Discoverability by allowing Wallets to generate push subscriptions independently from the Dapp Client being available.

Instead the Dapps will host a DID document statically on their domain and the Cast Server will handle the push subscription and notify them with a webhook

---

EDIT

This PR is now including spec changes for 4 milestones included in the Stage 1 (Discoverability Stage) from our 3-stage Push API refactor documented here

• Change Cast server and Notifier relationship
• Allow Wallets to independently subscribe to Dapps
• Introduce notification types for filtering
• Enable Wallets to update subscriptions

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[llbartekll]

this did:web at a first glance looks pretty fancy but tbh I am not fully convinced with key exchange here.

just for the sake of highlighting the purpose...
what are the pros?:

• all goes through the relay, we can see a tag
• ?

[Rakowskiii]

Should all registered webhooks get info about all the subscriptions? Or how do I know which webhook is for which project?
Do they just call <cast_url>/<project_id>/register_webhook?

Should this be protected by some auth, so that malicious actor can't change webhook for dapp?

[bkrem]

Wording:

Suggested change

	Not every message is the same and not every wallet user wants to receive every possible push notification that a dapp targets their wallet account.
	Not every message is the same and not every wallet user wants to receive every possible push notification that a dapp targets in their wallet account.

[bkrem]

Definition above states seconds resolution but this is in milliseconds. Do we want seconds?

[bkrem]

Wording

Suggested change

	A Push Subscription will include a claim labelled `scp` with a string value include the user authorized notification types separated by whitespaces.
	A Push Subscription will include a claim labelled `scp`, with a string value that represents the user-authorized notification types separated by whitespaces.

[bkrem]

Wording:

Suggested change

	A Push Message will include a parameter called `type` in the message payload which indicates the notification type is being delivered to the wallet user
	A Push Message will include a parameter called `type` in the message payload which indicates the notification type being delivered to the wallet user.

[TalhaAli00]

maybe we should be explicit and just put the rest of the information here instead of ...otherClaims

[TalhaAli00]

Suggested change

	The Push subscribe flow will require a dapp to host a static json file which will contain a DID document compliant with `did:web` method as specified [here](https://w3c-ccg.github.io/did-method-web/). In this DID document we will specify a X25519 public key that will be used by the Push API protocol to derive a symmetric key for the Push topic.
	The Push subscribe flow will require a dapp to host a static json file which will contain a DID document compliant with `did:web` method as specified [here](https://w3c-ccg.github.io/did-method-web/). In this DID document, we will specify a X25519 public key that will be used by the Push API protocol to derive a symmetric key for the Push topic.

[TalhaAli00]

Suggested change

	On the Wallet side we will be able to fetch a list of dapps that expose public keys for Push subscribe from a registry as for example our WalletConnect Cloud Explorer. These public keys are generated on the Cast server which will be able to listen for new subscriptions sent by the wallet to the subscribe topic which is the sha256 hash of the public key exposed.
	On the Wallet side, we will be able to fetch a list of dapps that expose public keys for Push subscribe from a registry as for example our WalletConnect Cloud Explorer. These public keys are generated on the Cast server which will be able to listen for new subscriptions sent by the wallet to the subscribe topic which is the sha256 hash of the public key exposed.