New python-fastapi generator (#9611)

* [python-fastapi] Added new generator

See https://fastapi.tiangolo.com/ for more details about FastAPI

Signed-off-by: Nikita Vakula <programmistov.programmist@gmail.com>

* [python-fastapi] Added samples

Signed-off-by: Nikita Vakula <programmistov.programmist@gmail.com>

samples/server/petstore/python-fastapi/README.md

@@ -0,0 +1,29 @@
+# OpenAPI generated FastAPI server
+
+This Python package is automatically generated by the [OpenAPI Generator](https://openapi-generator.tech) project:
+
+- API version: 1.0.0
+- Build package: org.openapitools.codegen.languages.PythonFastAPIServerCodegen
+
+## Requirements.
+
+Python >= 3.6
+
+## Installation & Usage
+
+To run the server, please execute the following from the root directory:
+
+```
+    pip3 install -r requirements.txt
+    uvicorn main:app --host 0.0.0.0 --port 8080
+```
+
+and open your browser at `http://localhost:8080/docs/` to see the docs.
+
+## Running with Docker
+
+To run the server on a Docker container, please execute the following from the root directory:
+
+```bash
+docker-compose up --build
+```