Update configuration.mdx based on issue #266

Author: kgowru

fern/products/sdks/overview/python/configuration.mdx

@@ -11,7 +11,7 @@ groups:
   local:
     generators:
       - name: fernapi/fern-python
-        version: 0.7.1
+        version: ^4.24.0 # Required for SDK variables support
         config:
           client:
             class_name: "YourClient" 
@@ -23,6 +23,10 @@ groups:
 </ParamField>
 
 <ParamField path="client" type="ClientConfiguration" default="ClientConfiguration()" required={false} toc={true}>
+  The client configuration object allows you to customize the generated client class. Available options:
+  
+  - `class_name`: Name of the generated client class
+  - `sdk_variables`: Automatically inject variables into endpoint paths from client initialization
 </ParamField>
 
 <ParamField path="default_bytes_stream_chunk_size" type="number" default="null" required={false} toc={true}>
@@ -32,6 +36,19 @@ groups:
 <ParamField path="exclude_types_from_init_exports" type="bool" default="false" required={false} toc={true}>
 </ParamField>
 
+<ParamField path="extension_headers" type="object" default="{}" required={false} toc={true}>
+  Add custom extension headers to API requests. Headers can be specified in OpenAPI using `x-fern-sdk-variables`. For example:
+
+  ```yaml
+  x-fern-sdk-variables:
+    project_id:
+      type: string
+      description: "The project ID to use for all requests"
+  ```
+
+  The variable will be automatically injected into endpoint paths that contain the matching parameter name.
+</ParamField>
+
 <ParamField path="extra_dependencies" type="object" default="{}" required={false} toc={true}>
   If you want to add custom dependencies to your generated SDK, you can specify them using this configuration. For example, to add a dependency on boto3, your config would look like:
   ```