Rebase `securedrop@signal-proto-focal` against latest `develop`

[eloquence]

Let's keep the prototype in securedrop's signal-proto-focal branch up-to-date with securedrop@develop.

1. [x] Initial rebase
2. [x] #28
3. [ ] freedomofpress/signal-groups#2
   • [ ] see also: freedomofpress/securedrop-e2e@use-cfm-signal-groups
4. [x] Runnable!
   1. [x] python journalist.py
   2. [x] python journalist2.py
   3. [x] Source can create Source Interface account
   4. [x] Source can read automatic replies from journalist[2].py
   5. [x] Source can submit a message
   6. [x] Source can read automatic replies from journalist[2].py

[cfm]

I don't seem to have privileges in this repository to edit the ticket's title or description, so I'll note here for the record that what's due for a rebase, while it is in the scope of securedrop-e2e, is actually securedrop's signal-proto-focal branch.

[conorsch]

@cfm updated perms, you (all all other SD maintainers) should be good to go now! It still makes sense to me conceptually to track the work in this ticket, but you're right that the changes must be made in another repo.

[cfm]

Initial rebase done and pushed to my fork. Now logging blocking issues and tracking them at the top of the ticket.

[cfm]

As of cfm/securedrop@4e8682d, the journalist[2].py scripts and the Source Interface can register with the journalist and source APIs, respectively. I have a bit more diffing and fixing to do next week to get things working end-to-end, then a re-rebase to make the changes in signal-proto-focal logical with the Refactor scrypt hashing and source app session mgmt PR series:

1. freedomofpress/securedrop#5692
2. freedomofpress/securedrop#5694
3. freedomofpress/securedrop#5695

[cfm]

As of cfm/securedrop@dd00aba, the demo flow again works end to end. I propose to:

1. push Jen's signal-proto-focal (https://github.com/freedomofpress/securedrop/commit/08068350941d22e02e8f041ffcb958635da704db) to a new archive branch signal-proto-focal-from-v2.0.0; and then
2. force-push my fork cfm/securedrop@signal-proto-focal to the canonical freedomofpress/securedrop@signal-proto-focal.

Since this is a rebase, there's no meaningful merge possible that could be reviewed in a pull request, but I'm open to suggestions for how else we might review (2).

[cfm]

This is done as proposed in https://github.com/freedomofpress/securedrop-e2e/issues/27#issuecomment-970644484:

cfm@ozymandias{1227:128}$ git log --pretty=full -n 1 origin/signal-proto-focal-from-v2.0.0
commit 08068350941d22e02e8f041ffcb958635da704db (origin/signal-proto-focal-from-v2.0.0, signal-proto-focal-from-v2.0.0)
Author: redshiftzero <jen@redshiftzero.com>
Commit: redshiftzero <jen@redshiftzero.com>

    fix: updating API to work with latest crate (rebase fallout)
cfm@ozymandias{1228}$ git log --pretty=full -n 1 origin/signal-proto-focal
commit dd00aba70929d0cb8eebf1b871324e81a5d6c9b2 (HEAD -> signal-proto-focal, origin/signal-proto-focal, cfm/signal-proto-focal)
Author: redshiftzero <jen@redshiftzero.com>
Commit: Cory Francis Myers <cory@freedom.press>

    fix: updating API to work with latest crate (rebase fallout)