Extend Http base class with config interface and add optional chaining to the Client

[letelete]

This PR is a proposal for implementing fluent interface experience provided by the SDK.

Chained methods (withLocale) are optional, don't break usage of the SDK, and are backward compatible.

Moreover, a configuration can be overridden on endpoint calls by passing particular params (eg. locale).

This proposal suggests a base PoC for refactoring the SDK and enabling the user to provide initial configuration on the makeClient function call level such as Bearer token, Currency, and more...