"Upload codelist" functionality in component config

[nkylstad]

Description

WHY:

As a user, I want to be able to upload an existing (static) codelist to my app when I need to use it in a component.

In scope

Only adding the "Upload codelist" button in the "Add codelists" tab, allowing user to select a JSON codelist file to upload.

Out of scope

• "Select from library" or any other UI changes shown in the sketches.
• Adding metadata like codelist name and description

Sketches

Tasks

• Implement "upload codelist" button
• Remove texts explaining how to manually upload codelist via Gitea

Additional information

We have a similar button to upload datamodel, can we re-use (and possibly make a Studio-component)?

Acceptance criteria

• It is possible to upload a codelist from codelist tab when configuring options for a component
• When the codelist is uploaded it is also selected as option property for the component
• The uploaded codelist is available to select for other options components

[wrt95]

Find out if we need validation on frontend or backend or both

[Konrad-Simso]

I've noticed that the PR does not fulfill all acceptance criteria.

• The uploaded file is not selected automatically.
• There is no real validation other than JsonSerializer. If it fails the api sends a error code of 500 to the frontend, which is not ideal.

[ErlingHauan]

Testing

Nice work 👏
Tested with various valid and invalid code lists, and it works as expected.

One comment:
When uploading an invalid file, this is the error message:

The backend responds with 400 and the message:

The JSON value could not be converted to System.Collections.Generic.List`1[Altinn.Studio.Designer.Models.Option]

Could we act on this message and display a more specific message in the toast? Maybe something like:

Filen du lastet opp har ikke gyldig format.