Add browser_launch_opts config option

[srcrip]

This adds a new browser_launch_opts configuration option that allows passing additional arguments to Playwright's browserType.launch().

Example usage:

config :phoenix_test,
  playwright: [
    browser_launch_opts: [
      args: [
        "--use-fake-ui-for-media-stream",
        "--use-fake-device-for-media-stream"
      ]
    ]
  ]

There are existing options for messing with the Page Context and Browser Context, I'm not a playwright expert so I'm not even 100% on how these things differ, and the playwright API is quite complex, but basically although there's a lot of overlap here, you can't use those configs to edit what is actually sent to playwright when you start the browser process--which is what you need to do if you want to pass cli level flags to the browser.

The background on this is at Jump, where we use your library quite a bit, we have a react powered audio recorder interface that does not load properly in our playwright tests. I realized we could actually get it to initialize properly if we pass the --use-fake-ui-for-media-stream and -use-fake-device-for-media-stream flags to the browser when playwright initializes it.

Obviously every playwright API is a little different, and in this library we have this pattern of configuring a lot of stuff in the global config + the overrides in exunit tags, so that seemed like a good way to go about it.

This kinda page is the closest to some kind of official documentation on this on the playwright docs site, but its also not very well documented even in playwright itself that you can do this. In fact they kind of discourage you from doing it almost, but it does in fact work: https://playwright.dev/docs/api/class-browsertype#browser-type-launch

[ftes]

Nice, I like it.

Thanks Andrew, also for taking the time to describe your use case.
I find that very valuable as reference.

Just some minor comments before we get this in.

[srcrip]

thanks for the fast response @ftes, I just commited a better test and I'll make the changes you requested here.

[srcrip]

ok @ftes, feel free to review now.

[srcrip]

also, do you want me to create a PR to playwright_ex as well documenting this on that side? Right now it works because playwright_ex allows these undocumented configs, but it would probably be good to document it as well.

[ftes]

Beautiful, I like the integration test.

Couple more suggestions/questions.

[srcrip]

ok ready again @ftes

[ftes]

👍

[ftes]

Beautiful, let's get this merged.

also, do you want me to create a PR to playwright_ex as well documenting this on that side? Right now it works because playwright_ex allows these undocumented configs, but it would probably be good to document it as well.

Sure, would be great to document args and maybe other options that BrowserType.launch accepts.

[ftes]

Looks like we have to skip these for websocket connection.