Store partyId locally

[Andreass2]

Description

• Stores partyId in our local db to avoid a new request on each event. Getting partyId can be a bottleneck, so this will improve performance.

Related Issue(s)

• Lagre PartyId i broker db for å unngå unødvendige spørringer til Altinn.Register #345

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)
• All tests run green

Documentation

• User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

[Andreass2]

Also updated test for resource, as duplicate now gives 400 error.