Update testing to allow for modal test

[stefpiatek]

• went for slimming down the dev FHIR server to only minimal required, as we're not using this in production
• found the source of why tests were flaky! - turns out by default tests are ran in parallel, might be worth looking in the jest documentation to see if there's a way to mark individual tests as having to be run sequentially, otherwise using the command line flag that I've set for npm test should work
• Updated some of the test setup so that the modal should then be able to work during testing. Might be worth experimenting to see if we need to have any timeout at all now that we're not running tests in parallel