Enable venv in project

[tetienne]

To ease the project installation process for the developers, a nice feature of Poetry is to create a virtual env directly in the project.
See https://python-poetry.org/docs/configuration/#virtualenvsin-project-boolean

Most of the IDE automatically detects it and uses it.

~/git/synologydsm-api enhancement/venv-in-project                                                          
❯ poetry install                                                                                           Creating virtualenv synologydsm-api in /home/tetienne/git/synologydsm-api/.venv                            
Installing dependencies from lock file                                                                                                                                                                                
Package operations: 83 installs, 0 updates, 0 removals                                                                                                                                                                
  • Installing smmap (3.0.4)                                                                                 • Installing zipp (3.3.1)                                                                                
  • Installing certifi (2020.6.20)                                                                           • Installing chardet (3.0.4)                                                                             
  • Installing gitdb (4.0.5)                                                                                 • Installing idna (2.10)                                                                                 
  • Installing importlib-metadata (2.0.0)                                                                    • Installing markupsafe (1.1.1)                                                                          
  • Installing mccabe (0.6.1)                                                                                • Installing pbr (5.5.1)                                                                                 
  • Installing pycodestyle (2.6.0)                                                                           • Installing pyflakes (2.2.0)                     
...