Add support for SSE in the MockClient

[ryber]

The MockClient does not yet support SSE. Add it

[codingkiddo]

Hi @ryber, I’d like to take this one.

Before I start, I want to confirm the expected MockClient API for SSE support.

My initial idea is to add a mock expectation API that can return one or more ServerSentEvent / event-stream messages for Unirest.sse(url).connect(...), with regression tests covering both synchronous and async SSE consumption.

Would you prefer:

1. extending the existing expect(...).thenReturn(...) style for SSE, or
2. adding a dedicated SSE-specific mock response builder?

Happy to follow the existing MockClient style and keep the first PR focused on basic SSE event streaming support.

[ryber]

Hey yea sure @codingkiddo, You can try and get it working with expect...I think that would be ideal, but I suspect you might need a dedicated method

[codingkiddo]

Thanks! I’ll start by trying to support SSE through the existing expect(...) API first.

My initial plan is to allow something like mock.expect(GET, url).thenReturn(...) with a text/event-stream response body, and have Unirest.sse(url).connect(...) consume that mocked response.

If this becomes awkward or leaks too much SSE-specific behavior into the normal response API, I’ll explore a dedicated method as a follow-up.