✨ Add support for tag metadata in OpenAPI (#1348)

* Allow to add OpenAPI tag descriptions

* fix type hint

* fix type hint 2

* refactor test to assure 100% coverage

* 📝 Update tags metadata example

* 📝 Update docs for tags metadata

* ✅ Move tags metadata test to tutorial subdir

* 🎨 Update format in applications

* 🍱 Update docs UI image based on new example

* 🎨 Apply formatting after solving conflicts

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

tests/test_tutorial/test_metadata/test_tutorial004.py

@@ -0,0 +1,65 @@
+from fastapi.testclient import TestClient
+
+from metadata.tutorial004 import app
+
+client = TestClient(app)
+
+openapi_schema = {
+    "openapi": "3.0.2",
+    "info": {"title": "FastAPI", "version": "0.1.0"},
+    "paths": {
+        "/users/": {
+            "get": {
+                "tags": ["users"],
+                "summary": "Get Users",
+                "operationId": "get_users_users__get",
+                "responses": {
+                    "200": {
+                        "description": "Successful Response",
+                        "content": {"application/json": {"schema": {}}},
+                    }
+                },
+            }
+        },
+        "/items/": {
+            "get": {
+                "tags": ["items"],
+                "summary": "Get Items",
+                "operationId": "get_items_items__get",
+                "responses": {
+                    "200": {
+                        "description": "Successful Response",
+                        "content": {"application/json": {"schema": {}}},
+                    }
+                },
+            }
+        },
+    },
+    "tags": [
+        {
+            "name": "users",
+            "description": "Operations with users. The **login** logic is also here.",
+        },
+        {
+            "name": "items",
+            "description": "Manage items. So _fancy_ they have their own docs.",
+            "externalDocs": {
+                "description": "Items external docs",
+                "url": "https://fastapi.tiangolo.com/",
+            },
+        },
+    ],
+}
+
+
+def test_openapi_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == openapi_schema
+
+
+def test_path_operations():
+    response = client.get("/items/")
+    assert response.status_code == 200, response.text
+    response = client.get("/users/")
+    assert response.status_code == 200, response.text