Service integration and more

[jsheunis]

Apart from some styling and UX updates, this PR mainly advances the service integration functionality, i.e. fetching metadata from a configurable endpoint, and pushing updated metadata to a configurable endpoint.

Summary:

• Adds configurable opt-in functionality for fetching data from service endpoints. The main changes include:
  • new additions to the config file to opt in to this function and to provide the endpoints with parameterization
  • including functions for fetching data in the main shaclvue component (multiple records of a class, and a single record by id) and the InstancesSelectEditor.
  • adding the actual request funcitonality to the graphdata composable. This changes the workflow to return promises which is also why the dynamic component instantiation code in the propertyshapeeditor has to be wrapped in a suspense tag.
  • a new update to read additional prefixes from config
• Adds base functionality for user to add a token: adds the composables and components and further functions for asking for a token to be entered when a user opts to submit their edited data. The token is stored in sessionStorage and subsequently made part of any future GET or POST request to the configured service. Submit button is a simple icon in the app header bar.
• WIP functionality for form submission:
  • io is updated to allow POST requests using the fetch-lite package
  • io now handles error responses in an improved way
  • formdata composable is updated to include generalised functionality for handling conversion of form data to quads in an rdf.dataset (TODO: refactor the existing saveForm funcitonality to use this)

Form submission is now ready to be tested locally.