Usability of syncron and asyncron services could be better

[nklamann]

I would very much like to use openapi-python-generator as a black box where the output directory of openapi-python-generator can be deleted at will and its content is the sole responsibility of the generator.

I would like to work in the following iterative process:

• predelete / create the output directory of openapi-python-generator
• start openapi-python-generator with options
• correct some mistakes with a script if required (*)
• use the result
• ... repeat until satisfied

At the moment this is not the case:

I must edit <directory>/services/.__init__.pyand import either theasync services or the others. Even your tutorial example requires this step.

I would prefer a command-line option to define whether asyncronous or syncronous services shall be generated. This would play nicely with the other command-line options for format and linrary. The whole generation process gets predictable and is only dependent of command line switches.

(*) I have some syntax errors , for example these https://github.com/MarcoMuellner/openapi-python-generator/issues/30