using dependency injection for API server, for cleaner code

[ZibanPirate]

Is your feature request related to a problem? Please describe.
The code inside the api folder is a bit messy...

Describe the solution you'd like
One way to improve it, is to use one of the strategies of IoC, which is dependency injection.
since this is a Nodejs server, we can use an npm package to handle dependency injection, the library i recommend is: typedi

Describe alternatives you've considered
There are other way to improve it too, like using a framework on top of express (eg: Nest.js)

Additional context
N/a

Feature Branch : feat/cleaner-api
Feature PR : #283

[well-balanced]

I'd like to tackle with this issue. is there a dead line? 🧐

[ZibanPirate]

Please go ahead, if you know what to do, I will support you on it

[well-balanced]

I created a PR related with loader as a first step. please give me a feedback 😊

[well-balanced]

I've looked over the api codes. but I couldn't find dependencies for each service functions. could you give me an example?

[ZibanPirate]

i will create a feature branch, with a sample code containing DI, we will start from there

[ZibanPirate]

closing as done in #283