Resolving circular imports for protocols

[kangz12345]

Problem

When apps communicate with each other, they need to know the message protocol of each app.
For convenience and robustness, many apps will provide dataclass protocols to dumps and loads messages.

However, when an app A and B needs the protocol of each other, they must import each other, which leads to circular import.
Circular import is not good because:

• it may not run at all
• pylint rejects it
• it introduces unnecessary dependency

Therefore, we need a way to break through this problem.

Suggestion

Recommend to define such protocols outside the main module, i.e., make an independent module for protocols.

iquip apps

For the apps included in iquip, make such protocols in a "protocol" module.
For example, if we have app modules app1.py and app2.py, their protocol definitions are defined in protocol.py.
Then protocol.py will never import the other app modules, so it will not cause any circular imports.

Third-party apps

For the external apps which are not included in iquip, they can implement it however they want, since iquip does not import them.
They can import iquip.protocol and use it without any problem.

[BECATRUE]

I also found out how to prevent circular imports, but there may be another neat way..
So, your opinion looks the best solution.

Furthermore, we need two functions; dumps and loads, then how about implementing them in utils.py.

[kangz12345]

Oh, they are available in qiwi (or whatever it will become), so we don't have to implement it again!

[kangz12345]

Even though we can also make new ones in this repository for some reasons (e.g., we need more features, etc.), I still think they should be in protocol.py because they are dedicated to protocol encoding and decoding.

[BECATRUE]

Ah, I forgot it completly.. And your opinion looks better because they are also related to protocols!