asset uploader: delete uploaded asset

[jdsika]

situation

After uploading an asset with dependencies in the externalArtifacts a user would like to delete this simulation asset again

problem/solution

Currently the delete button is not working as it is unclear if the deletion must cascade or not.

Cases:

1. An asset has no externalArtifacts
   No issue. Just delete the asset and all associated uploaded data. As long as it is not minted there was also no upload to IPFS

2. An asset has an externalArtifact
   We are talking about externalArtifacts which are comeplete "SimulationAssets" and not e.g. single external files on a public repository or similar. (see scenario asset example)

2.1) The externalArtifact is already minted
An already minted asset cannot and shall not be deleted. Just delete the respective asset on which the user clicked.

2.2 The externalArtifact is part of the uploaded assets
Just delete the asset. It may be the case that the asset in externalArtifacts is useful by itself amd a user wants to upload it.

2.3) The externalArtifact is missing
-> provide a warning to the user that the artifact is missing (I guess we said it should not fail? "error")

3. delete simulation asset which is needed and referenced as externalArtifact by another uploaded asset
   Deleting an item should re-trigger the check if there are externalArtifact missing/available and maybe notify the user that the deleteion of an asset results in a missing externalArtifact as in 2.3)