Find a work around for cookiecutter when already in git tracked directory

[ArBridgeman]

Summary

When we create a new project using the cookiecutter template or adapt it for an existing project, we will often run into issues, as already the directory is tracked by git. So when a user gets to this step, they get the shown error message:

❯ cookiecutter https://github.com/exasol/python-toolbox.git \
       --checkout 3.0.0 --directory sqlglot-toolbox
You've downloaded /home/xxx/.cookiecutters/python-toolbox before. Is it okay to delete and re-download it? [y/n] (y): y
A valid repository for "https://github.com/exasol/python-toolbox.git" could not be found in the following locations:
/home/xxx/.cookiecutters/python-toolbox/sqlglot-toolbox

Based on a experience and an initial check, it seems like many of our users are:

1. Using the cookiecutter in another directory
2. Copying over what was done in Prepare initial release #1 to the directory managed by git

It would be ideal if we:

• Check that cookiecutter does not provide an easy work around or override
  --> if they do, we should update the documentation
• Create a common command, potentially wrapped in a nox session within the PTB
  --> this would perform the operations users are already doing but in a temporary directory

Tasks

• Check cookiecutter options
• Create a common command (nox sessions) to perform these operations
• Update the Getting Started & other parts of the User Guide
• Check / adapt / add on to project-template integration tests