Add multimodel custom fileextension support

[zhcn000000]

Description

Add support for custom extensions for multimodal language model FileURLs and BinaryContents or add parameters that do not perform file extension verification. For example, I want to be able to pass in extensions such as .pptx and .odt , .ods or other opendocument xml format document for DocumentUrl when sending documents to the model or sending cad file as ImageUrl to model which is rendered to image in server and The model server may have a custom multimedia decoder or document parser that allows the input of multimedia files of types other than predefined ones
On the other hand, if the model server does not support decoding multimedia in a specified format or parsing documents in a specified format, such as not supporting parsing doc or xls files, you can also customize the extension to add options to prevent the sending of these extensions

References

No response

[DouweM]

@zhcn000000 I agree the current lists of extensions and media types are too restrictive. We could use https://docs.python.org/3.14/library/mimetypes.html to support essentially all file types, and rely on the error from the model if it's sent something it doesn't support.

Would you be up for submitting a PR, as you know exactly what types and model APIs you're dealing with and can verify the new code works for you?