API endpoint to PATCH Assets, to modify tags

We would like to modify the tags for certain assets, but the current endpoint is of type PUT, meaning, it is a complete overwrite of the tags.

This means, that an asset with 10+ tags will be overwritten to only one tag, if you're not careful.

With PATCH, it is much safer, since we can make sure to only update the specific tags we want to create or modify.

This also removes a lot of edge case troubleshooting.