Missing .eml Extension in the file name and Null MIME Type for .eml Attachments

Describe the bug

When retrieving .eml file attachments using the Microsoft Graph SDK for Outlook mail items, the attachment name does not include the .eml extension, and the content-type/mime-type is returned as null. This results in improper handling of .eml files on the client side.

Expected behavior

When fetching .eml attachments, the expected output should include:

The attachment name should be formatted as attachment.eml.
The content-type/mime-type should be message/rfc822 or similar, indicating that the file is an email message.

Expected behaviour with the example of pdf file and the existing behaviour for .eml file

How to reproduce

Make an API call to retrieve a message that contains an .eml attachment using the endpoint:
GET https://graph.microsoft.com/v1.0/me/messages/{messageId}/attachments
Identify an attachment with the .eml type from the response.
Call the endpoint to get the content of the attachment:
GET https://graph.microsoft.com/v1.0/me/messages/{messageId}/attachments/{attachmentId}/$value
Observe that the name of the attachment does not include the .eml extension and that the content-type/mime-type is null.

SDK Version

5.16.0

Latest version known to work for scenario above?

No response

Known Workarounds

No response

Debug output

</details>


### Configuration

_No response_

### Other information

_No response_

Start by reproducing the issue with GET /v1.0/me/messages/{messageId}/attachments and the attachment $value endpoint for an .eml file. The payload names no repository files or tests; done means the returned attachment name includes the .eml extension and its content type is message/rfc822 or similar.