Make Krona plots viewable in data portal

[naglepuff]

Fix #1707

Changes

Backend

A new API endpoint has been added to allow a client to obtain the URL for specific types of data objects. This is necessary because the existing endpoint is only accessible to authenticated (i.e. logged in) users. The Krona plot's HTML needs to be accessible for all users. Being logged in should not be required to view these data objects.

This endpoint accepts a data_object_id and returns the URL for the HTML for that data object only if the data object has a specific file_type. If this endpoint is used to try and obtain the download URL for a non-Krona plot data object, it return a 400. Tests have been added for this endpoint.

Frontend

Krona plots are now viewable on the data portal without the need to log in or click the download button. They are accessible by clicking the magnifying glass icon in the corresponding row:

Clicking will bring up a modal (implemented with a v-dialog component) containing an iframe.

[codytodonnell]

Overall this looks and works great. Also thanks for adding tests for the new API endpoint. The one issue I raised could be addressed at a later time if we find it important.

I'll also note that I had to do a git pull --rebase to pull down the latest changes. I'm not sure if that will be the case for others pulling down these changes once they are in main.