RUMM-788 Add data scrubbing API

[ncreated]

What and why?

🚚 This PR adds RUM events scrubbing feature with set of 4 new public APIs:

public func setRUMViewEventMapper(_ mapper: @escaping (RUMViewEvent) -> RUMViewEvent?)
public func setRUMResourceEventMapper(_ mapper: @escaping (RUMResourceEvent) -> RUMResourceEvent?)
public func setRUMActionEventMapper(_ mapper: @escaping (RUMActionEvent) -> RUMActionEvent?)
public func setRUMErrorEventMapper(_ mapper: @escaping (RUMErrorEvent) -> RUMErrorEvent?)

Each API allows the user to inspect and modify RUM events before they get send. Returning nil drops the event.

How?

A basic interface of EventMapper is introduced:

internal protocol EventMapper {
    func map<T: Encodable>(event: T) -> T?
}

and plugged into DataProcessor's pipeline, just before writing the event to the file.

It is implemented by RUMEventsMapper which intercepts each value using closures configured by the user in the public interface.

In the next PR I will also add test scenario to Example application with the integration test for scrubbing API.

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

[buranmert]

can we use model generator to create these mocks too?

[ncreated]

I was thinking of this, but it took me ~10 min to do it by hand, while adding this in rum-models-generator would be at least few hours. Let's see how difficult would it be to maintain this hand-made mocks, if too expensive, we can invest our time in rum-models-generator 👌.