Adding support for v2 api version.

[alexcottner]

Adding support for v2 api version.

Need to:

• Add support for v2 routes in dev-tools
• Add support for v2 routes in kinto-http-client (link)
• Publish new kinto-http-client to firefox (link)
• Figure out a reasonable UI for this
• Update tests

This will require mozilla/remote-settings#1104 to be deployed for forwards compatability.

[leplatrem]

If we want to gradually migrate our clients from v1 to v2, shouldn't we have a pref on the client instead, and do there what you do here in the devtools:

const apiVersion = Services.prefs.getCharPref("api_version", "/v1");
const serverUrl = new URL(SERVER_URL, apiVersion);

[alexcottner]

shouldn't we have a pref on the client instead

I was thinking leaving that as a single pref in services.settings.server and allowing it to be overridden in it's entirety. That feels simpler or am I wrong?

Splitting it in two for the dev-tools UI just feels easier because instead of a single dropdown with 14 options we have two dropdowns. (and if/when we make a v3 it would be 21)

[leplatrem]

We haven't really found a design that would allow us to gradually roll out clients to v2

The changes of this PR work to try things out on nightly or when running the client with MOZ_REMOTE_SETTINGS_DEVTOOLS=1. But won't be able to also support our api version migration later

A potential idea would be to use a separate preference on the client:

Services.prefs.setIntPref("services.settings.api_version", 2);

And on the client have something like:

let apiVersion = Services.prefs.getIntPref("services.settings.api_version");
apiVersion = [1, 2].contains(apiVersion) ? apiVersion : 1;

and do the concatenation on the client code

[leplatrem]

This won't work on beta/release because of this code:
https://searchfox.org/firefox-main/rev/14c08f0368ead8bfdddec62f43e0bb5c8fd61289/services/settings/Utils.sys.mjs#53-76

[alexcottner]

Ah yes, need to adjust that logic.

[alexcottner]

Added to my patch here: https://phabricator.services.mozilla.com/D277258