Use or autodetect MIMEType of file and give it an extension

[antonizoon]

Signal has a MIMEType for each image in its sqlite database which is reliable enough to write file extensions for. This is critical since Windows for example relies solely on file extensions to detect file type, and HTTP servers typically does the same.

As can be seen in Signal-back, it writes file extensions for attachment filenames to disk:

https://github.com/xeals/signal-back/blob/7b9bc2112afa24316da1e2c515e067f69f91d5c4/cmd/extract.go#L116

While I would try to use signal-back instead, it crashes on backup dumps of my size (3-5GB).

[mutlusun]

Hello,

this is fixed in the latest version.