Validate Blocked Words File

Validate a blocked_words YAML file content.

Args: request: Dictionary with 'file_content' key containing the YAML string

Returns: Dictionary with 'valid' boolean and either 'message'/'errors' depending on result

Example Request:

{
    "file_content": "blocked_words:\n  - keyword: \"test\"\n    action: \"BLOCK\""
}

Example Success Response:

{
    "valid": true,
    "message": "Valid YAML file with 2 blocked words"
}

Example Error Response:

{
    "valid": false,
    "errors": ["Entry 0: missing 'action' field"]
}