Add HTTPService and AsyncLoop for microservice

[letonghan]

Description

The framework and base class for microservices.

Expected behavior

Start an HTTP (fastapi) service using async loop. User could customize microservice based on HTTPService class.

Test

Tested on local server.

Usage

from async_loop import AsyncLoop
args = {
    'name': 'test_loop',
    'cors': False,
    'protocol': 'http',
    'port': 8080,
    'host': 'localhost',
    'runtime_args': {        
        'title': 'test_service',
        'description': "this is a test."
    }
}
loop = AsyncLoop(args)
with loop:
    loop.run_forever()