GUI OPIs: Check to see if the IBEX GUI can read OPIs from a server

As someone developing OPIs for use in the IBEX client, I want to be able to get the OPIs from the server (see #6562 for the discussion), and to be sure that this can be achieved I need to test the supposition that this can be done.

## Acceptance Criteria
- [ ] There is a very simple http server that serves a single OPI
- [ ] A dev client is configured to read that server and get that OPI
- [ ] If the client cannot read the OPI from the web server close the following tickets with the comment `System will not be able to use this functionality`:
- [ ] #7089
- [ ] #7090
- [ ] #7091
- [ ] #7093
- [ ] If the client cannot read the OPI from the web server, create a new ticket along the lines of #6562 which specifies that the webserver method will not work as required

## Notes
- This is a proof of concept test, and should not be added to the repo, rather notes should be added to the other tickets listed to be closed if this isn't possible as required
- Review should probably be undertaken as an "over the shoulder" look to see how and if the OPI is read than a PR and merge
- The [comment ](https://github.com/ISISComputingGroup/IBEX/issues/6562#issuecomment-853991910) on the disucssion ticket has some insights for this