Setup a redis container in Platform cluster

[SandGrainOne]

Description

There is a need for a caching mechanism that can cache items across multiple pods in the Platform. During analysis of #3637 we landed on using redis in a docker container as part of the Platform cluster.

In this issue we need to identify the requirements for the redis instance. Security consideration, backup or other things. There will be need for a custom configuration.

There are currently two issues that needs this type of caching:

• Register person number lookup
• Storage Get instances continuation tokens.

Resources:
https://redis.io/topics/quickstart
https://hub.docker.com/_/redis/
https://redis.io/documentation

Considerations

Configuration of Redis. For example the need for password protection?
Storing of configuration as a secret like how it's being done with connection information to KeyVault?
Need for backup? redis has persistence that we probably don't need.

Acceptance criteria

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Specification tasks

• Development tasks are defined

Development tasks

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Test

Add test cases here as checkboxes that are being tested as part of the changes.

Definition of done

Verify that this issue meets DoD (Only for project members) before closing.

• Documentation is updated (if relevant)
  • Technical documentation (docs.altinn.studio)
  • User documentation (altinn.github.io/docs)
• QA
• Manual test is complete (if relevant)
• Automated test is implemented (if relevant)
• All tasks in this userstory are closed (i.e. remaining tasks are moved to other user stories or marked obsolete)