[FxA] The "Sign In" promo is wrongly displayed on a non-owner shot if it's opened on the Firefox profile where you are already logged

[SoftVision-CosminMuntean]

[Affected versions]:

• Nightly 65.0a1
• Screenshots 34.0.0 dev

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a Screenshots FxA account with at least one saved shot.
• Have a profile where you are already logged in Screenshots FxA account.

[Steps to reproduce]:

1. Open the Firefox browser with the profile from prerequisites.
2. Open a saved shot created on a different profile (eg: this link).
3. Observe the shot page.

[Expected result]:

• The "Sign In" promo is not displayed.

[Actual results]:

• The "Sign In" promo is displayed even if you are already logged in.

[ Notes]:

• Here is a screen recording of the issue:
  

[punamdahiya]

Attached PR with the fix

[SoftVision-CosminMuntean]

I have verified this issue with latest Screenshots (34.0.0) dev version and the issue is no longer reproducible on a received shot.
But, I have noticed that the "Sign In" promo is still displayed if you navigate to a non-owner shot that has been deleted or has expired.

[Prerequisities]:

• The latest Screenshots dev version is installed on a Firefox profile.
• You are already logged with a valid FxA account.

[Steps to reproduce]:

1. Open the Firefox browser with the profile from prerequisites.
2. Navigate to an expired shot or deleted shot that was made on another profile (eg: this one).
3. Observe the page.

[Expected result]:

• The "Sign In" promo is not displayed.

[Actual results]:

• The "Sign In" promo is displayed even if you are already logged in.

Here is a screen recording of the issue:

[punamdahiya]

@SoftVision-CosminMuntean Thanks for catching this, we should pass accountId cookie info (hasFxa) in not found pages https://github.com/mozilla-services/screenshots/blob/master/server/src/pages/not-found/view.js#L32, will submit the PR

[SoftVision-CosminMuntean]

I have verified this issue using the latest Screenshots (34.0.0) dev version and is no longer reproducible. Tested on Windows 7 x64, Mac 10.13 and Arch Linux 4.12.