This PR removes a broken attempt to handle extension mismatches.

Problem

The code currently tries to verify if a file's mimetype (as determined by Android's ContentResolver) matches the mimetype inferred from the file's extension. If there is a mismatch, that might indicate that the file has the wrong extension, and the correct extension is appended.

String mimeType = applicationContext.getContentResolver().getType(contentUri);
MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
// this variable is misleadingly named, and should read 'mimetypeFromFilename'
String extensionFromFilename = mimeTypeMap.getMimeTypeFromExtension(
    MimeTypeMap.getFileExtensionFromUrl(fileName)
);

if (extensionFromFilename == null || !extensionFromFilename.equals(mimeType)) {
    fileName += "." + mimeTypeMap.getExtensionFromMimeType(mimeType);
}

However, MimeTypeMap.getFileExtensionFromUrl(fileName) will always returns null,
since getFileExtensionFromUrl takes URLs to always contain a /,
but *nix forbids / in filenames.

As a result, this check incorrectly appends an extra extension to
every filename it encounters (e.g. example.mp3.mp3).

Why remove the check

While the code is easily fixed, I think the check is better left out altogether, since in its current form, it is probably a truism. The value of mimeType is determined by applicationContext.getContentResolver().getType(contentUri), which internally calls mimeTypeMap.getMimeTypeFromExtension on the uri's extension.¹ This mimeType variable is then compared to the output of the exact same function (mimeTypeMap.getMimeTypeFromExtension). Hard for that to be wrong.

Better leave handling misleading extensions to Kodi. In my tests, Kodi and standalone ffmeg are more than capable of handling files with incorrect extensions over http. I tested this by using Kore to play back a mpeg encoded file with an incorrect extension (.flac).