Add template-consolidation component for buster

[conorsch]

Status

Ready for review

Description of changes

Using a dedicated "component" so that we can isolate ongoing development
specifically on template consolidation work [0] so that we can evaluate
upgrade behavior. While it's frankly acceptable to break "apt-test"
packages temporarily, we need the ability to test before/after states to
evaluate behavior during upgrades. Thus the separate component.

Requires updates to the CD logic that runs on apt-test.

Towards freedomofpress/securedrop-workstation#471

Contains newly built packages based on changes in freedomofpress/securedrop-builder#198

Checklist

• Confirm newest securedrop-proxy version available in the "main" pool is some nightly of 0.3.0: https://apt-test.freedom.press/pool/main/s/securedrop-proxy/
• Confirm newest securedrop-proxy version available in the "template-consolidation" pool is at least 0.3.1 (included in this PR): https://apt-test.freedom.press/pool/template-consolidation/s/securedrop-proxy/

Confirming the above, since apt-test is currently tracking this feature branch, is essentially verifying the following apt cache output:

securedrop-proxy:
  Installed: (none)
  Candidate: 0.3.1+buster
  Version table:
     0.3.1+buster 500
        500 https://apt-test.freedom.press buster/template-consolidation amd64 Packages
     0.3.0-dev-20201005-060258+buster 500
        500 https://apt-test.freedom.press buster/main amd64 Packages

except you don't have to mangle your apt sources locally.

[conorsch]

Example from a local container. The package securedrop-workstation-grsec is present in both the "buster/main" component, as usual, and the new "buster/template-consolidation" component, but the newly created package securedrop-workstation-viewer (cf. freedomofpress/securedrop-workstation#615) is available only in "buster/template-consolidation":

root@4c4d15475eb0:/# apt-cache policy securedrop-workstation-grsec
securedrop-workstation-grsec:
  Installed: (none)
  Candidate: 4.14.186+buster2
  Version table:
     4.14.186+buster2 500
        500 https://apt-test.freedom.press buster/main amd64 Packages
        500 https://apt-test.freedom.press buster/template-consolidation amd64 Packages
root@4c4d15475eb0:/# apt-cache policy securedrop-workstation-viewer
securedrop-workstation-viewer:
  Installed: (none)
  Candidate: 0.1.0+buster
  Version table:
     0.1.0+buster 500
        500 https://apt-test.freedom.press buster/template-consolidation amd64 Packages

Hopefully that'll make testing upgrade behavior for consolidation a bit easier.

[conorsch]

Marking as ready-for-review. I propose we merge these changes into the apt-test "main" branch, so that we can continue to iterate on packages specifically related to freedomofpress/securedrop-workstation#471 , while preserving the regular apt-test setup in use in many different contexts.

[conorsch]

Debs for 1.6.0~rc2 are visible on apt-test: https://apt-test.freedom.press/pool/main/s/securedrop-app-code/ Mentioning because apt-test is currently tracking this feature branch, which has been rebased to include #66

[zenmonkeykstop]

Confirmed via apt-cache in a VM. LGTM