Migrate FetchService to Gloo project

[jstarry]

When rethinking the Fetch service, we should consider implementing for the gloo project. See here for the relevant issue: rustwasm/gloo#4

[teymour-aldridge]

So I think the key thing is to introduce a mechanism for handling callbacks into gloo. I think what makes sense is to introduce a callback mechanism into gloo which very closely mirrors Yew's and stick some From<yew::Callback> implementations into gloo behind a feature flag.

With that done it should be a fairly easy lift (after adding some things like a builder syntax).

I'm happy to do this.

[hamza1311]

Why do you think gloo should be based on callbacks for something like fetch? async functions work well and are more idiomatic Rust. Those can be used from Yew like any other future.

[teymour-aldridge]

Oh that's totally true. It's just that the current code we have works with callbacks, but rewriting it to use async does make more sense :D

[hamza1311]

FetchService is no longer present here so can we close this? The issue in the gloo repo can be used to track this.