Missing CONTROL value in MessageType enum causing validation errors

[MykhailoSadruk]

The Glean Python SDK is missing the CONTROL value in the MessageType enum, which causes Pydantic validation errors when the API returns messages with messageType: "CONTROL".

Steps to Reproduce
Use the Glean Python SDK to retrieve a chat that contains messages with messageType: "CONTROL"

Call client.client.chat.retrieve(id=chat_id)

SDK throws validation error

Expected Behavior
The SDK should successfully parse messages with messageType: "CONTROL" without validation errors.

Actual Behavior
Response validation failed: 1 validation error for Unmarshaller
body.chatResult.chat.messages.4.messageType
Input should be 'UPDATE', 'CONTENT', 'CONTEXT', 'DEBUG', 'DEBUG_EXTERNAL', 'ERROR', 'HEADING', 'WARNING' or 'SERVER_TOOL' [type=enum, input_value='CONTROL', input_type=str]

API Endpoint: /rest/api/v1/getchat

Proposed Fix
Add CONTROL = "CONTROL" to the MessageType enum in glean/api_client/models/chatmessage.py:

class MessageType(str, Enum):
UPDATE = "UPDATE"
CONTENT = "CONTENT"
CONTEXT = "CONTEXT"
DEBUG = "DEBUG"
DEBUG_EXTERNAL = "DEBUG_EXTERNAL"
ERROR = "ERROR"
HEADING = "HEADING"
WARNING = "WARNING"
SERVER_TOOL = "SERVER_TOOL"
CONTROL = "CONTROL" # Missing value

Impact
This is a breaking issue that prevents users from retrieving chat history when messages contain the CONTROL type, which appears to be returned by the Glean API in certain scenarios.