✨ Add support for Pydantic models in Form parameters (#12129)

Revert "⏪️ Temporarily revert "✨ Add support for Pydantic models in `Form` pa…"

This reverts commit 8e6cf9ee9c.

docs_src/request_form_models/tutorial001.py

@@ -0,0 +1,14 @@
+from fastapi import FastAPI, Form
+from pydantic import BaseModel
+
+app = FastAPI()
+
+
+class FormData(BaseModel):
+    username: str
+    password: str
+
+
+@app.post("/login/")
+async def login(data: FormData = Form()):
+    return data

docs_src/request_form_models/tutorial001_an.py

@@ -0,0 +1,15 @@
+from fastapi import FastAPI, Form
+from pydantic import BaseModel
+from typing_extensions import Annotated
+
+app = FastAPI()
+
+
+class FormData(BaseModel):
+    username: str
+    password: str
+
+
+@app.post("/login/")
+async def login(data: Annotated[FormData, Form()]):
+    return data

docs_src/request_form_models/tutorial001_an_py39.py

@@ -0,0 +1,16 @@
+from typing import Annotated
+
+from fastapi import FastAPI, Form
+from pydantic import BaseModel
+
+app = FastAPI()
+
+
+class FormData(BaseModel):
+    username: str
+    password: str
+
+
+@app.post("/login/")
+async def login(data: Annotated[FormData, Form()]):
+    return data