viewevents POST request sent twice for page views within "scoped" themes

[Atmire-Kristof]

Describe the bug

When a theme is configured for a given handle, object pages within this theme will (inconsistently) send out two "viewevents" POST requests instead of just one, upon page visit.

To Reproduce

Steps to reproduce the behaviour:

• Configure a theme for an object handle (see example configuration below)
• Visit the page of an item that falls under the object handle (e.g. the handle points towards a parent community of said item)
• In the Network tab, you should see two "viewevents" POST requests (filter by method:POST to notice easier). This is not consistent, but to my experience, happens most of the time. It depends a bit on how fast the initial page load is (see more info below for the cause).

Example configuration:

themes:
  - name: custom
    extends: dspace
    handle: 123456789/1
  - name: dspace

Tip: You can use the configuration above, connected to the demo instance and visiting the Publications community and/or any of its collections or items.

Expected behaviour

Only one "viewevents" POST request should be sent per page view.

Cause

The reason it's sending out two requests instead of one, is because requests are sent when the ViewTrackerComponent is loaded for an object page, but the theme configuration causes a reload of the contents, causing the component to be recreated a second time.

Possible fixes

I see two solutions, with the second option being less desired than the first, but might be a good fallback:

• Prevent DSO page contents from loading before the theme is fully resolved. This would however mean longer loading screens, but in turn no flashing reload.
• Prevent the ViewTrackerComponent sending a request when it detects it's not on the correct theme yet. This is possible by querying the ThemeService to check what the currently active theme is and comparing that against whatever Theme resolves from the DSpaceObject.

[ybnd]

↑ we'd like to tackle this one