Add mkt_tok marketing tokens

[Seanstoppable]

No description provided.

[jparise]

Looks good. Thanks, @Seanstoppable!

[fmarier]

By the way, the mkt_tok parameter is actually required for unsubscribe links to work: brave/brave-browser#9018 (comment)

[jparise]

@fmarier I haven't seen any recent updates to the linked issue. Were you able to determine if removing this token merely makes the unsubscribe process less convenient (by not prefilling the email address) or if it prevents unsubscribing entirely?

[fmarier]

Were you able to determine if removing this token merely makes the unsubscribe process less convenient (by not prefilling the email address) or if it prevents unsubscribing entirely?

No, I don't have enough visibility over the backend to be able to know for sure, though having to type an email address manually also makes for a bad user experience and so I'm planning to exempt these unsubscribe requests from the filter built into Brave.