Create controller and service for options/code lists

[ErlingHauan]

Description

In this PR an OptionsController and an OptionsService has been created.
The OptionsService uses the AltinnAppGitRepository to manipulate the options files.

5 4 new endpoints have been added:

• GET an array of the names of all option lists from a repo
• GET a single option list from a repo
• POST a single option list to a repo
• PUT a single option list to a repo
• DELETE a single option list from a repo

Considerations

• I was unsure what to call the methods, e.g. GetOptions, GetOptionLists or GetCodeLists. What do you think?
• I'm not 100% sure if my usage of CancellationToken is correct. Please keep it in the back of your mind when reviewing.
• These endpoints only handle static code lists. Is there a need for endpoints for dynamic code lists?

Related Issue(s)

• Endpoint for adding, updating and deleting codelist in Studio (app-context) #12873

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required) - tested OK with Postman when temporarily disabling [AutoValidateAntiforgeryToken]
• Relevant automated test added (if you find this hard, leave it and we'll help out)

[standeren]

Looks very good! Impressive testing and documenting 😮‍💨

I have some questions concerning the need for 404 and duplicated error messages, as well as some nitpicking conserning naming 😅

Also I wonder if we should give the testfiles in the OptionsControllerTests more specific name like GetOptionsTests and CreateOptionsTests etc.

[standeren]

Very nice work!! 👏