Added toBuilder methods to Request

[kringol]

Changes for #1672

@slandelle These are the simple/minimum changes.

But there is the fact that the constructors of RequestBuilder that take a prototype remain and could be used directly, breaking again the purpose of this change.
But in order to overcome that a more impactful change (backwards incompatible) has to be made. But I would leave that decision to you or your opinion on it.

• Ideal: moving the RequestBuilder as an inner class of Request or DefaultRequest and restricting access to those methods
• Not ideal: Making those constructors protected at least to reduce the chances of usage directly, but still poses a risk

Bonus question:
Do you prefer the implementation of toBuilder methods as default implementation on the interface or as it is now on the DefaultRequest.java?

[slandelle]

We can’t introduce a breaking change on such core API atm.
The best we can do is flag as deprecated.

[slandelle]

Please address comments.

[kringol]

We can’t introduce a breaking change on such core API atm.
The best we can do is flag as deprecated.

Flagged both constructors as deprecated for now then. And suppressed the deprecation warning on the interface default implementation for the time being. If that doesn't sound good, I can just remove the deprecation and hope people will not use it directly

[slandelle]

Thanks!