DCJ-519: Log dar application state changes

[rushtong]

Addresses

Partially addresses https://broadworkbench.atlassian.net/browse/DCJ-519

See also: #2633

Summary

This PR adds mixpanel events for all of the major Data Application Request states: create, update, attest, and submit. Events are visible in the dev mixpanel project:

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[aarohinadkarni]

looks good 👍

[fboulnois]

looks good 👍