chore(pyclient): move code interacting with server to new file

[YpeZ]

Issue

The code in client.py is exceeding 1000 lines, making maintenance troublesome at times.
Most of this code is for interacting with a server whilst it is also contains the class with which the users of the Pyclient interact.

Solution

Handling requests, parsing data and other processes that occur behind the scenes should be moved to a new file, e.g. _client.py, such that the client.py only serves for interacting with the user of the package.
This improves maintainability of the code as it makes a clear distinction between the code a user interacts with and code that runs behind the scenes and connects to the server.

Alternatives

No response

Additional context

No response

[YpeZ]

Integrated in other story