[Mobile Payments] PR suggestions to neaten up badging the Payments menu

[joshheald]

          💯 

Should we wrap this line in a method? Sort of "bind/observe badge changes"?

Originally posted by @iamgabrielma in #9812 (comment)

          Same as `HubMenuViewModel`: Should we wrap this line in a method? Sort of "bind/observe badge changes"?

Originally posted by @iamgabrielma in #9812 (comment)

Perhaps for another PR: Should we abstract this class into some PromotionChecker protocol to keep it detached from the specific TTP promotion checker? It could make sense also inject the protocol in the initializer for testability and to use this common protocol in the future for other feature announcements.

Originally posted by @iamgabrielma in #9812 (comment)

Same comment as with MainTabViewModel regarding abstracting this class into a protocol, as would seem that we're leaking implementation details about the badges into the HubMenu navigation coordinator responsibility.

Originally posted by @iamgabrielma in #9812 (comment)

All these are worth doing, but lower priority than other current work. We should certainly consider doing it this way rather than removing all the badge code when Tap to Pay is promoted enough.