Depends on D12155

after device list has been updated, secondary device should get a nonce from the keyserver, sign it, and then log in to identity

i also took this chance to introduce a helper function to get the device key upload

successfully logged in to identity and got an access token

checked that the device key upload contents were all present and looked correct. the one-time keys are marked as published in the helper function, but i will have to mark the prekeys as published after the identity service call in the next diff.