Fix react-sdk issue where isLoggedIn being set to false after successful token refresh

[JakeLo123]

What is this PR and why do we need it?

Fixing issue #166.

This should ensure that the main provider for the react-sdk doesn't flip isLoggedIn when a token refresh is successful by placing the code to getNewCore inside the provider to keep it in the react life cycle. Using a mutable ref object.

@synedra -- tagging you as a reviewer in case you'd like to take a look and make sure I didn't mistake your nice work on the dispose method. If I've misconstrued something, please let me know.

Pre-Merge Checklist (if applicable)

• Unit and Feature tests have been added/updated for logic changes, or there is a justifiable reason for not doing so.

[synedra]

This looks good to me. Thank you so much for doing this!

[synedra]

Forgot to approve

[dmackinn]

@synedra can you re-approve when you have a moment, Jake pushed up an update to address linting concerns after the original approval.

[synedra]

Sorry I missed that one! Thanks for fixing...

[MaxDNG]

Well done! If I may add, I think the config object should still be destructured. As it stand, because the rest operator is used, we retrieve a new config object on each re-render, making the useMemo not really useful.
The two options I see is either to extract all keys of the config from the FusionAuthProvider props, or to move it to a single config props. I think the second option is less desirable as it introduces a breaking change and puts the responsibility of maintaining the object reference (memoization) to the user.

[JakeLo123]

@MaxDNG That's a good suggestion -- I've pushed a commit to use destructuring instread of the rest operator to get the config.

I was able to tell that this regression happened on commit 6bbb2a7 -- a commit that I made 😅 -- where we switched the definition of FusionAuthProvider to use destructuring. I'm honestly not sure how exactly that causes this behavior but it is indeed the cause.

If anyone would like to observe it for yourself...

• Check out to commit 657c18d and observe that the isLoggedIn behavior is correct.
• Then checkout 6bbb2a and observe the behavior is buggy.
• Switch back to 657c18d and destructure the config object, either in a useMemo body or on the lines where you pass the properties into new SDKConfig
• Observe that the behavior is correct.

[JakeLo123]

@synedra -- sorry I keep dismissing your PR approval.

[alex-fusionauth]

Tested locally, thanks @JakeLo123 and @MaxDNG for jumping in!!