Docs: update instructions to install deps with Poetry

docs/user/build-customization.rst

@@ -326,15 +326,24 @@ Take a look at the following example:
      jobs:
        post_create_environment:
          # Install poetry
-         # https://python-poetry.org/docs/#osx--linux--bashonwindows-install-instructions
-         - curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python -
+         # https://python-poetry.org/docs/#installing-with-the-official-installer
+         - curl -sSL https://install.python-poetry.org | python3 -
          # Tell poetry to not use a virtual environment
-         - $HOME/.poetry/bin/poetry config virtualenvs.create false
-         # Install project's dependencies
-         - $HOME/.poetry/bin/poetry install
+         - $HOME/.local/bin/poetry config virtualenvs.create false
+       pre_install:
+         # Export project dependencies to requirements.txt
+         - $HOME/.local/bin/poetry export --with docs > docs/requirements.txt
 
    sphinx:
      configuration: docs/conf.py
+
+   python:
+     install:
+       # Install exported dependencies
+       - requirements: docs/requirements.txt
+       # Optional: install current package if imported from `docs/conf.py`
+       - method: pip
+         path: .
 
 
 Override the build process