add: demo server and client

demo_server/demo_client/.travis.yml

@@ -0,0 +1,17 @@
+# ref: https://docs.travis-ci.com/user/languages/python
+language: python
+python:
+  - "3.7"
+  - "3.8"
+  - "3.9"
+  - "3.10"
+  - "3.11"
+  # uncomment the following if needed
+  #- "3.11-dev"  # 3.11 development branch
+  #- "nightly"  # nightly build
+# command to install dependencies
+install:
+  - "pip install -r requirements.txt"
+  - "pip install -r test-requirements.txt"
+# command to run tests
+script: pytest --cov=openapi_client