TAARDIS: Pass hashed client id to TAAR via AMO API request

As TAAR moves away from being a shield study instead of receiving the client-id via a query string set by the add-on the client-id will be available in hashed form as a cookie a HTTP header sent by the browser.

Bug with the details of the Firefox implementation is here: https://bugzilla.mozilla.org/show_bug.cgi?id=1489531

This bug is to cover reading that cookie header and passing the hashed id down to TAAR via the AMO api.

For QA: this change will only work in the context of about:addons, so you have to update the discoverURL pref to https://discovery.addons-dev.allizom.org/%LOCALE%/firefox/discovery/pane/%VERSION%/%OS%/%COMPATIBILITY_MODE% (for -dev).

Then:

• set your own client ID to a test ID that returns recommendations, e.g., 00000000-0000-0000-0000-000000000000. You can change the client ID in /path/to/current FF profile/datareporting/state.json:

  • open FF and navigate to about:profiles

  • find “This is the profile in use and it cannot be deleted.” and open the root directory

  • open datareporting/state.json and replace the content of this file with:

    {"clientID":"00000000-0000-0000-0000-000000000000"}
    

  • restart your browser

• open about:addons and load the disco pane
• you should get recommdations

If you repeat those steps with 00000000-aaaa-0000-0000-000000000000, you should not have the recommendations but a different list with editorial choices.

[willdurand]

@muffinresearch, do we still need a feature flag then if we have a check for disco?

I think it would be safer in case we need to disable it if something goes wrong.

[muffinresearch]

@rebmullin @willdurand This will need to go into prod next week to make the 29th January deadline so we’ll want to get this config’d on for stage and prod ahead of the Monday tag.