Add reactivity to oauthClient

[jjnesbitt]

Previous to this change, the "logout" button would not change to "login" if clicked (it wasn't reactive). Logout would still be performed, but the text wouldn't change, leading to a situation where clicking "logout" actually logs you in.

It's a small change but IMO the main benefit is in displaying how to correctly use the oauth client. It's also possible this is the wrong approach, in which case I'm open to suggestions.

[subdavis]

I don't think this is the right way to add reactivity to this state.

• The OauthClient library itself should probably be a vue instance that chooses specific properties (such as user state) to be reactive rather than making an unfamiliar class instance reactive(), which might have weird side effects. vue-project-template shouldn't be responsible for peering into the black box of OauthClient.
• If this isn't possible, then reactivity should be layered in before provide: { oauthClient } in main.ts in this template, because otehrwise you're making a shallow copy of the client in Home.vue and using oauthClient anywhere else in the app won't do anything.

[subdavis]

FWIW: do not add a vue dependency to OauthClient: it will make a 2-to-3 transition much harder. Let's resolve this in here.

[brianhelba]

I think it'd be out of scope to add anything Vue-specific to the OAuthClient anyway. The OAuthClient is intended to be framework-agnostic. If there are standardized things that'd make reactivity easier downstream, that might be more acceptable.