Define process how to patch earlier versions of nugets

## Description

There is a possible scenario in the future that there will be released patches for security issues that will force us to update the Altinn.app nuget packages.

For the applications owners using the latest versions it would then typical be little issue to upgrade.

The problem if there is a old app with old version. Upgrading to latest would probably causes some breaking changes.

Problem: Should we patch older versions of nuget packages? If so how many versions?

## In scope
- Define and document process for updating old versions.
- Include in SLA documentation?

No files or tests are named; start by locating the existing SLA documentation and current package-release guidance. Document the agreed policy for supporting and patching older NuGet versions, including the update process and the versions covered.

Written by the indexing model from the issue text.