Auth-module: Support for plain Fetch API

[Timkor]

Is your feature request related to a problem? Please describe.

Users might not use axios or @nuxt/http - particularly with the new Nuxt polyfill for fetch.

It would be good to support the plain Fetch API, since it's already polyfilled by Nuxt.

Describe the solution you'd like to see

Do not load any networkHandler if set to false and default to the Fetch API.

auth: {
  networkHandler: false,
},

[Atinux]

I think it's planned for the v5 already.

[nathanchase]

Or what about the ability to use https://github.com/nuxt-contrib/ohmyfetch instead of axios?