chore(dev-launcher) - Change the default context to oauth_webchannel_v1

This is the default flow that we use in desktop today, but we can't
remove the old flow until ESR is updated to v140+.

Fixes FXA-9872

Author: jonalmeida

packages/fxa-dev-launcher/README.md

@@ -11,7 +11,7 @@ Available options:
 - `FIREFOX_DEBUGGER=true` - open the [Browser Toolbox](https://developer.mozilla.org/en-US/docs/Tools/Browser_Toolbox) on start (NOTE: `false` by default for speed).
 - `FXA_DESKTOP_CONTEXT` - context value for the fxa-content-server: `context=[value]` (NOTE: `fx_desktop_v3` is default).
 
-Tip: run `FXA_DESKTOP_CONTEXT=oauth_webchannel_v1 yarn firefox` (from the repo root) to test the OAuth Desktop flow. Run `FXA_DESKTOP_CONTEXT=oauth_webchannel_v1 FIREFOX_BIN=/Applications/Firefox\ Nightly.app/Contents/MacOS/firefox yarn firefox` to test the OAuth Desktop flow (for MacOS) on Nightly.
+Tip: run `FXA_DESKTOP_CONTEXT=fx_desktop_v3 yarn firefox` (from the repo root) to test the old Desktop flow (supported until ESR 140). Run `FXA_DESKTOP_CONTEXT=fx_desktop_v3 FIREFOX_BIN=/Applications/Firefox\ Nightly.app/Contents/MacOS/firefox yarn firefox` to test the Desktop flow (for MacOS) on Nightly.
 
 ### Basic Usage Example in OS X
 

packages/fxa-dev-launcher/profile.mjs

@@ -47,7 +47,7 @@ const CONFIGS = {
 };
 
 const env = process.env.FXA_ENV || 'local';
-const FXA_DESKTOP_CONTEXT = process.env.FXA_DESKTOP_CONTEXT || 'fx_desktop_v3';
+const FXA_DESKTOP_CONTEXT = process.env.FXA_DESKTOP_CONTEXT || 'oauth_webchannel_v1';
 const e10sDisabled = process.env.DISABLE_E10S === 'true';
 let fxaEnv = CONFIGS[env];
 
@@ -115,11 +115,11 @@ const fxaProfile = {
   // allow webchannel url, strips slash from content-server origin.
   'webchannel.allowObject.urlWhitelist': fxaEnv.content.slice(0, -1),
   'browser.tabs.firefox-view': true,
+  // TODO in FXA-11026, see if we still need the other prefs since we only need
+  // to use the autoconfig to get everything else set. See: bug 1942925.
   'identity.fxaccounts.autoconfig.uri': fxaEnv.content,
   // disable password auto-fill; we typically don't need to test this daily.
   'signon.rememberSignons': false,
-  // TODO in FXA-9872, make oauth_webchannel_v1 the default context and
-  // change these values for fx_desktop_v3. (Also, update the README note)
   ...(process.env.FXA_DESKTOP_CONTEXT === 'oauth_webchannel_v1' && {
     'identity.fxaccounts.oauth.enabled': true,
     'identity.fxaccounts.contextParam': 'oauth_webchannel_v1',