Validate pyproject.toml of echo client python sample

Author: 4c0n

.github/workflows/samples-python-client-echo-api.yaml

@@ -7,6 +7,18 @@ on:
       - samples/client/echo_api/python-disallowAdditionalPropertiesIfNotPresent/**
       - .github/workflows/samples-python-client-echo-api.yaml
 jobs:
+  validate-pyproject-toml:
+    name: Validate pyproject.toml
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+      - name: Install validator
+        run: pip install 'validate-pyproject[all]'
+      - name: Validate
+        run: validate-pyproject samples/client/echo_api/python/pyproject.toml
   build:
     name: Test Python client
     runs-on: ubuntu-latest