isLoading should default to true even when doing SSR

[adamjmcgrath]

Description

I originally thought isLoading should initialize as false when doing SSR, the logic being that the SDK will never start loading during SSR so isLoading didn't make sense to be true

However, the output of SSR rendering is rendered on the client, to be hydrated, so a client will expect it to be initialised as true. If it's false, then immediately hydrated as true you get Warning: Expected server HTML to contain a matching <div> in <div>. because it's been rendered in a different state that the ReactDom.hydrate is expecting.

Whilst this will change initial rendering behaviour, it shouldn't break anyone - just remove the warning.

References

fixes #182

Testing

I've changed the SSR tests to use ReactDOMServer.renderToString rather than renderHook because renderHook still expects to be called in a jsdom environment.

• This change adds test coverage for new/changed/fixed functionality

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not master