RUMM-1785 DatadogEventBridge implemented

[buranmert]

What and why?

As part of WKWebView tracking, Datadog iOS SDK needs to communicate with Datadog Browser SDK.

How?

DatadogEventBridge is implemented as a mean of communication between those two platforms.
It receives messages from Browser SDK, parses them into JSON and forwards to corresponding WebEventConsumer (Log or RUM).

NOTE

Also, an extension of WKUserContentController is added in order to inject DatadogEventBridge into the WKWebView. However, I can't find a way to test this extension in unit tests. I tried webView.evaluateJavaScript(...) API to call JS methods within the webview, yet that didn't work in unit tests (although it works in Example app).
We may need to test this extension in integration tests.

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference

[ncreated]

I left few questions, about the architecture plan (vs upcoming V2 efforts), threading and testing.

IMO this can't be single-threaded feature, as Browser events are equally complex to mobile events and we should process them on a background queue.

[ncreated]

What will be the lifecycle of DatadogMessageHandler? As I understand, it will be created with public API similar to:

controller.addDatadogMessageHandler(allowedWebViewHosts: ["datadoghq.dev"])

and destroyed when? I'm trying to guess the lifecycle of underlying queue - assuming it will be destroyed when WebView disappears, it should be fine.