📝 Add Header docs

docs/tutorial/header-params.md

@@ -0,0 +1,54 @@
+You can define Header parameters the same way you define `Query`, `Path` and `Cookie` parameteres.
+
+## Import `Header`
+
+First import `Header`:
+
+```Python hl_lines="1"
+{!./tutorial/src/header-params/tutorial001.py!}
+```
+
+## Declare `Header` parameteres
+
+Then declare the header parameters using the same structure as with `Path`, `Query` and `Cookie`.
+
+The first value is the default value, you can pass all the extra validation or annotation parameteres:
+
+```Python hl_lines="7"
+{!./tutorial/src/header-params/tutorial001.py!}
+```
+
+!!! info
+    `Header` is a "sister" class of `Path`, `Query` and `Cookie`. It also inherits from the same common `Param` class.
+
+!!! info
+    To declare headers, you need to use `Header`, because otherwise the parameters would be interpreted as query parameteres.
+
+## Automatic conversion
+
+`Header` has a little extra functionality on top of what `Path`, `Query` and `Cookie` provide.
+
+Most of the standard headers are separated by a "hyphen" character, also known as the "minus symbol" (`-`).
+
+But a variable like `user-agent` is invalid in Python.
+
+So, by default, `Header` will convert the parameter names characters from underscore (`_`) to hyphen (`-`) to extract and document the headers.
+
+Also, HTTP headers are case-insensitive, so, you can declare them with standard Python style (also known as "snake_case").
+
+So, you can use `user_agent` as you normally would in Python code, instead of needing to capitalize the first letters as `User_Agent` or something similar.
+
+If for some reason you need to disable automatic conversion of underscores to hyphens, set the parameter `convert_underscores` of `Header` to `False`:
+
+```Python hl_lines="7"
+{!./tutorial/src/header-params/tutorial002.py!}
+```
+
+!!! warning
+    Before setting `convert_underscores` to `False`, bear in mind that some HTTP proxies and servers disallow the usage of headers with underscores.
+
+## Recap
+
+Declare headeres with `Header`, using the same common pattern as `Query`, `Path` and `Cookie`.
+
+And don't worry about underscores in your variables, **FastAPI** will take care of converting them.

docs/tutorial/src/header-params/tutorial001.py

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+from fastapi import FastAPI, Header
+
+app = FastAPI()
+
+
+@app.get("/items/")
+async def read_items(*, user_agent: str = Header(None)):
+    return {"User-Agent": user_agent}

docs/tutorial/src/header-params/tutorial002.py

@@ -0,0 +1,8 @@
+from fastapi import FastAPI, Header
+
+app = FastAPI()
+
+
+@app.get("/items/")
+async def read_items(*, strange_header: str = Header(None, convert_underscores=False)):
+    return {"strange_header": strange_header}

mkdocs.yml

@@ -28,6 +28,7 @@ nav:
         - Body - Schema: 'tutorial/body-schema.md'
         - Body - Nested Models: 'tutorial/body-nested-models.md'
         - Cookie Parameters: 'tutorial/cookie-params.md'
+        - Header Parameters: 'tutorial/header-params.md'
     - Concurrency and async / await: 'async.md'
     - Deployment: 'deployment.md'