Add tests.yml workflow

This commit creates the `tests.yml` workflow. It is responsible
for running all the tests which are exposed by `tox.ini`:

* Lint with `flake8`
* Check dependencies with `pipdeptree`
* Unit tests and coverage with `pytest`
* Static type checking with `pyright`

`flake8` and `pipdeptree` run only once, with Ubuntu and with the
latest Python version.

On the other hand, the unit tests and static type checkings are
run using a matrix of operating systems and Python versions.

References: BAR-133.

Signed-off-by: Israel Barth Rubio <israel.barth@enterprisedb.com>

.github/workflows/tests.yml

@@ -0,0 +1,133 @@
+name: Tests
+
+on:
+  pull_request:
+
+  push:
+
+  workflow_dispatch:
+    inputs:
+      source-ref:
+        description: Source code branch/ref name
+        default: main
+        required: true
+        type: string
+
+env:
+  SOURCE_REF: ${{ inputs.source-ref || github.ref }}
+  WORKING_DIRECTORY: ./pg_backup_api
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout the source code
+      uses: actions/checkout@v3
+      with:
+        ref: ${{ env.SOURCE_REF }}
+
+    - name: Set up Python
+      uses: actions/setup-python@v4
+      with:
+        python-version: 3.x
+
+    - name: Install tox
+      run:
+        pip install tox
+
+    - name: Run linter
+      working-directory: ${{ env.WORKING_DIRECTORY }}
+      run:
+        tox -e lint
+
+  dependency_checking:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout the source code
+      uses: actions/checkout@v3
+      with:
+        ref: ${{ env.SOURCE_REF }}
+
+    - name: Set up Python
+      uses: actions/setup-python@v4
+      with:
+        python-version: 3.x
+
+    - name: Install tox
+      run:
+        pip install tox
+
+    - name: Run dependency checker
+      working-directory: ${{ env.WORKING_DIRECTORY }}
+      run:
+        tox -e dep
+
+  unit_tests:
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+
+      matrix:
+        python-version:
+        - '3.7'
+        - '3.8'
+        - '3.9'
+        - '3.10'
+        - '3.11'
+
+    steps:
+    - name: Checkout the source code
+      uses: actions/checkout@v3
+      with:
+        ref: ${{ env.SOURCE_REF }}
+
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v4
+      with:
+        python-version: ${{ matrix.python-version }}
+
+    - name: Install tox
+      run:
+        pip install tox
+
+    - name: Run unit tests
+      working-directory: ${{ env.WORKING_DIRECTORY }}
+      run:
+        tox -m test
+
+  static_type_checking:
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+
+      matrix:
+        python-version:
+        - '3.7'
+        - '3.8'
+        - '3.9'
+        - '3.10'
+        - '3.11'
+
+    steps:
+      - name: Checkout the source code
+        uses: actions/checkout@v3
+        with:
+          ref: ${{ env.SOURCE_REF }}
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install tox
+        run:
+          pip install tox
+
+      - name: Run static type checks
+        working-directory: ${{ env.WORKING_DIRECTORY }}
+        run:
+          tox -m type