Track app domain as event property within app-initiated flows

[markmhendrickson]

Whenever an app initiates a wallet flow for the user, we should include a new property for all events triggered within that flow that contains the domain of the initiating app.

For example:

• App initiates user authentication
• App initiates transaction signing

The property should be included from the point of initiation until the closing of the relevant wallet window, and it should be included only for events that are triggered within that specific flow (and not, for example, for events triggered simultaneously in a separate window open for the wallet).

It could be named something like referringAppDomain and should include the complete base URL of the referring app (e.g. https://example.org not example.org/path/to/page).

This will enable us to measure the amount and types of wallet usage driven by particular apps.

[markmhendrickson]

I'm reopening since I'm unable to see the flowInitiatorURL come through in production, and my sense is that we need to modify this to flowInitiatorDomain for it to be most useful in report generation.

[edu-stx]

Ended up using the referringAppDomain property, and didn't update the screenshot. Is referringAppDomain available in the dashboard?

We can set whatever name is most convenient.

I'll update the comment on the PR to match the code.

[markmhendrickson]

Note that we ended up using property origin instead of referringAppDomain or flowInitiatorDomain and the value appears to be reported accurately in production.