Add integration tests (#53)

This PR adds integration test for the API client, service, as well as
handel. These tests are performed by creating, updating & deleting
orders on the simulation database.

As discussed in the latest team meeting, these tests were originally
written with the goal of automatising everything. As a consequence, some
of them might not be the most coherent: for instance
`test_list_public_trades()` just verifies that the returned list isn’t
null. It doesn’t check for the correctness of the output at all. These
tests might thus have to be split into system tests (that would be
performed manually), and integration test. 

Additionally, I think that
having these tests run by the CI is not the most appropriate (especially
given that they depend on other components than just the client).

So please suggest alternatives & improvements, & let's make a next level
robust, efficient and awesome test suite!😎

.github/workflows/integration_test.yml

@@ -0,0 +1,55 @@
+name: Electricity-Trading-API-Integration-Tests
+
+on:
+  workflow_dispatch:
+  release:
+    types: [published]
+
+env:
+  DEFAULT_PYTHON_VERSION: '3.11'
+
+jobs:
+  run-tests:
+    name: Integration tests
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-20.04
+        python:
+          - "3.11"
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Setup Git
+        uses: frequenz-floss/[email protected]
+
+      - name: Print environment (debug)
+        run: env
+
+      - name: Fetch sources
+        uses: actions/checkout@v4
+        with:
+          submodules: true
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python }}
+          cache: 'pip'
+
+      - name: Install required Python packages
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install -e .[dev-pytest]
+          pip freeze
+
+      - name: Run the integration tests
+        env:
+          API_KEY: ${{ secrets.API_KEY }}
+          GRIDPOOL_ID: ${{ secrets.GRIDPOOL_ID }}
+        run: |
+          pytest -vv integration_tests/
+        timeout-minutes: 10
+
+

RELEASE_NOTES.md

@@ -17,6 +17,8 @@
 * Remove dependency to `googleapis-common-protos`
 * Replace `Energy` with `Power` for the `quantity` representation
 * Add str function for `DeliveryPeriod` object
+* Add integration tests for the API
+* Add an equality function to the Order type
 
 ## Bug Fixes