No File Check When Uploading Channels to Asset in Wire Graph

[LeoNerdoG]

If user tries to upload a non-CSV Channels file in Wire Graph, Kura reports an error, which is OK, but the output could be messy (it depends on the type of the file and length of it - in my case I uploaded a .txt file with a lot of contents) - see the screenshot bellow.

Testflow:

1. Login to Kura as admin/admin
2. Go to Packages, install Wires-development-package from Eclipse Marketplace
3. Go to Wire Graph, create a wireAsset comonent and add a channel to it
4. Try to upload a random .txt file via "Upload channels" button
5. Observe the error message

Expected behavior I suggest that Kura checks if the uploaded file has a .CSV extension (although user can have an inappropriate .cvs file), this way we would take care of a lot errors.

Screenshot:

Target Environment (please complete the following information): Board: Raspberry Pi 3 OS version: Linux raspberrypi 4.19.75-v7+ # 1270 SMP Tue Sep 24 18:45:11 BST 2019 armv7l GNU/Linux Additional info: /

[LeoNerdoG]

Although this issue has PR #2912 linked, we have decided to keep it open, becasue it has not been fixed yet (see this comment)