Upgrade react-cookie for reliable cookie state

[kumar303]

For QA: please check for regressions in any feature that relies on a cookie:

• log in / log out
• A/B test for green/blue buttons Run A/B test for install button (green vs. blue) #12298
• The view classic desktop site link in the footer

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We need to upgrade react-cookie for better SSR support. See #12461 for details on how the older library is likely creating bugs.

[willdurand]

Raised to p2 because that seems like something we want sooner than later.

[kumar303]

Yeah, good point. We should probably do this before rolling out any new experiments.

[willdurand]

Upgrading was straightforward but Enzyme does not support the React Context API (not fully, not with shallow), which breaks some test cases...

[willdurand]

Documentation at: https://github.com/reactivestack/cookies/tree/master/packages/universal-cookie

[willdurand]

Upgrading was straightforward but Enzyme does not support the React Context API (not fully, not with shallow), which breaks some test cases...

I found a nice workaround and filed: #12625 to remove it once Enzyme supports the Context API.

[ioanarusiczki]

• log in / log out I tested with multiple accounts on AMO dev and AMO stage. I could log in and log out without issues.
• The A/B test was re-tested on AMO Stage and results are here
• after switching to view classic desktop then back to the new front end there's the mamo cookie's value is "on"

Cookies on AMO stage

Verified on AMO dev and AMO stage with FF63 - Win10