Horizon streaming support

[juanhurtado10]

ℹ️ This issue is an Epic

Context

Horizon provides a streaming mechanism for receiving events in near real-time. Instead of repeatedly sending requests to Horizon for batch updates, a connection is established between a client and Horizon with updates to an endpoint response streaming as new ledgers close and updates occur.

This reduces requests that return no data and allows near instantaneous updates client-side.

All attributes for the endpoints that allow streaming are the same as regular responses. A caller can initiate streaming by setting ‘Accept: text/event-stream’ in the HTTP header when making the request. Study an example of using streaming in the Follow Received Payments tutorial.

Objective

To add support for streaming requests with Horizon.

Checklist

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[csokun]

I played with streaming using Finch here the gist https://gist.github.com/csokun/b7fadda2a247075374ac2ca131b32fe6