TEMPORARY Introduce pre-commit workflow for consistency

.github/workflows/pytest.yaml

@@ -74,3 +74,17 @@ jobs:
         run: |
           source .venv/bin/activate
           pytest --cov-report xml:.coverage.xml --cov-report term --cov=ixmp4 -rsx --benchmark-skip
+
+  pre-commit:
+    name: Code quality
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+
+      - name: Force recreation of pre-commit virtual environment for mypy
+        if: github.event_name == 'schedule'  # Comment this line to run on a PR
+        run: gh cache delete $(gh cache list -L 999 | cut -f2 | grep pre-commit)
+        env: { GH_TOKEN: "${{ github.token }}" }
+
+      - uses: pre-commit/[email protected]

.pre-commit-config.yaml

@@ -0,0 +1,49 @@
+repos:
+# - repo: https://github.com/python-poetry/poetry
+#   rev: 30da950 #update this to next revision that include poetry-install
+#   hooks:
+#     -   id: poetry-check
+#     -   id: poetry-lock
+#     -   id: poetry-export
+#     -   id: poetry-install
+- repo: local
+  hooks:
+  - id: mypy
+    name: mypy
+    always_run: true
+    require_serial: true
+    pass_filenames: false
+
+    language: python
+    entry: bash -c ". ${PRE_COMMIT_MYPY_VENV:-/dev/null}/bin/activate 2>/dev/null; mypy $0 $@"
+    # additional_dependencies:
+    # - alembic
+    # - black
+    # - dask
+    # - fastapi
+    # - httpx
+    # - ipykernel
+    # - mypy
+    # - nbclient
+    # - pandas-stubs
+    # - pandera
+    # - psycopg[binary]
+    # - pydantic
+    # - pydantic-settings
+    # - pyjwt
+    # - pytest
+    # - python-dotenv
+    # - sphinx
+    # - sqlalchemy
+    # - types-toml
+    # - typer
+    # - xarray
+    args: ["."]
+- repo: https://github.com/psf/black
+  rev: 23.9.1
+  hooks:
+  - id: black
+- repo: https://github.com/astral-sh/ruff-pre-commit
+  rev: v0.0.292
+  hooks:
+  - id: ruff