Improve documentation for sessions and serving files (#24)

Author: RobertoPrevato

blacksheep/docs/sessions.md

@@ -67,7 +67,7 @@ sequenceDiagram
     Client->>Server: HTTP Request (Cookie: session ID)
     Server->>Store: Retrieve session data using session ID
     Store-->>Server: Session data
-    Server-->>Client: HTTP Response (may update Set-Cookie)
+    Server-->>Client: HTTP Response
 ```
 
 In this scenario, Session ID is exchanged between client and server via
@@ -137,6 +137,36 @@ Before version `2.4.0`, BlackSheep offered built-in support only for sessions
 stored entirely on the client side, in cookies. Using sessions with a different
 store required custom code.
 
+/// admonition | Cookies and cross-site request forgery.
+    type: danger
+
+When you store sessions in cookies on the client side, web applications must
+implement [Anti-Forgery validation](anti-request-forgery.md) to prevent
+Cross-Site Request Forgery (XSRF/CSRF).
+
+**Why?**
+
+Cookies are sent automatically by browsers with every request to your
+domain, making your app vulnerable to Cross-Site Request Forgery (CSRF)
+attacks, if information in cookies is used to authenticate requests and your
+application does not implement [Anti-Forgery
+validation](anti-request-forgery.md).
+
+**How?**
+
+Common anti-forgery mechanisms include:
+
+- CSRF tokens: Generate a unique token per session/request and require it in
+  forms or headers.
+- SameSite cookies: Set your session cookie with `SameSite=Strict` or
+  `SameSite=Lax` to limit cross-site requests.
+- Custom headers: For APIs, use and require a custom header (e.g.,
+  `X-Session-ID`) that browsers do not send cross-origin. In a user-defined
+  `SessionStore` type, you can rely on a custom request and response header to
+  exchange information with clients —updating your client code accordingly.
+
+///
+
 ## Enabling sessions, with custom store
 
 Starting from `2.4.0`, the built-in classes for sessions include support for

blacksheep/docs/static-files.md

@@ -1,4 +1,4 @@
-# Serving static files
+F# Serving static files
 
 This page covers:
 
@@ -28,21 +28,22 @@ When serving files this way, a match-all route ("*") is configured in the
 application router for `GET` and `HEAD`, and files are read from the configured
 folder upon web requests.
 
+
 It is also possible to serve static files from sub-folders:
 
 ```python
 app.serve_files("app/static")
 ```
 
-Enable file discovery (in such case, requests for directories will generate an
-HTML response with a list of files):
+To enable file discovery, add the `discovery=True` parameter. In such case,
+requests for directories will generate an HTML response with a list of files:
 
 ```python
 app.serve_files("app/static", discovery=True)
 ```
 
-BlackSheep also supports serving static files from multiple folders, and
-specifying a prefix for the route path:
+Serving static files from multiple folders is supported, using a different path
+for each folder:
 
 ```python
 app = Application()
@@ -52,6 +53,52 @@ app.serve_files("app/images", root_path="images")
 app.serve_files("app/videos", root_path="videos")
 ```
 
+### Route paths and folder names
+
+By default, when you serve files from a folder, the folder name is **not**
+included in the route at which files are served. For example, if you have a
+file `test.txt` in your `static` directory and you use:
+
+```python
+app.serve_files("static")
+```
+
+the file will be accessible at `http://localhost/test.txt` (not
+`http://localhost/static/test.txt`).
+
+If you want the files to be accessible under a specific route path (such as
+`/static/`), use the `root_path` parameter:
+
+```python
+app.serve_files("static", root_path="static")
+```
+
+With this configuration, `test.txt` will be accessible at `http://localhost/static/test.txt`.
+
+### Serving single files
+
+If you need to serve single files, it is possible to use the `file` function
+like in the following example.
+
+```python
+from blacksheep import Application, get
+from blacksheep.server.responses import file, ContentDispositionType
+
+
+app = Application()
+
+
+@get("/favicon.ico")
+def favicon_icon():
+    # Note: the file is read asynchronously and served in chunks,
+    # even though this function itself is synchronous
+    return file(
+        "path-to-your/favicon.ico",  # ← local path
+        "image/vnd.microsoft.icon",
+        content_disposition=ContentDispositionType.INLINE,
+    )
+```
+
 ## File extensions
 
 Only files with a configured extension are served to the client. By default,