⬆️ Update Pydantic to 0.21.0 (#90)

* ⬆️ Upgrade Pydantic and others (isort), update docs after changes by isort

* 🎨 Format with newest isort, update type hints in jsonable_encoder

* 🔧 Update test script, to avoid Pydantic type errors

* ⬆️ Update pyproject.toml with latest Pydantic

scripts/test.sh

@@ -13,7 +13,7 @@ fi
 
 export PYTHONPATH=./docs/src
 pytest --cov=fastapi --cov=tests --cov=docs/src --cov-report=term-missing ${@}
-mypy fastapi --disallow-untyped-defs
+mypy fastapi --disallow-untyped-defs --follow-imports=skip
 if [ "${PYTHON_VERSION}" = '3.7' ]; then
     echo "Skipping 'black' on 3.7. See issue https://github.com/ambv/black/issues/494"
 else