Allow sending and retrieval of additionalContext within authentication flow

[Shinsina]

REQUIRES parameter1/identity-x#54 TO BE MERGED AND DEPLOYED

From parameter1/identity-x#54: "This allows for the passthrough of a JSON object called additionalContext, this will allow for the newsletterSignupType (amongst other potential points of data) to be specified and returned namely for the login-link-click event tracking within P1 Events in order to enable correct event recording for reporting purposes."

[Shinsina]

Audience Acquisition Tab

[solocommand]

This looks fine as-is, barring changes from the IdX PR. It doesn't have any P1E interaction, so can you remove those screenshots and update the description please!

[solocommand]

Remove this, this will be present under additionalEventData.newsletterSignupType below

[Shinsina]

@solocommand This is how P1 Events expects it to be sent in order to send it accordingly via this: https://github.com/parameter1/base-cms/blob/master/packages/marko-web-p1-events/browser/index.js#L69

[Shinsina]

This looks fine as-is, barring changes from the IdX PR. It doesn't have any P1E interaction, so can you remove those screenshots and update the description please!

@solocommand

The IdX PR has no interaction with P1E, all that PR is intended to do is allow the retrieval of additional event data from the login link sent event in order for the corresponding click event to correlate to the correct sent location.

This PR is ultimately what interacts with P1E which is why those screenshots were included as they are.