Enable credentials support in Valkey for shared bucket in filter

[jordigilh]

Question

Which authN solution should be implemented for Valkey backend in the token rate limit filter introduced by #796 as part of #121

Context

#796 introduces Valkey as a backend to the token rate limit filter for M1, M2 and M6 milestones of #121 epic. However, the PR does not secure Valkey with authentication.

Approach

The spike would be to investigate which approach would be best fitting:

• mTLS
• Credentials provided by a secret
• Any other alternative

Deliverables

• Prototype for both approaches
• Security and operational cost: pros and cons of each approach
• Recommended solution.

Timebox

No response

Area

None

Parent Epic (optional)

No response

[alexsnaps]

This is a shared concern and probably is a "core" one even. If I'm not mistaken, the Praxis Policy Engine's session store already introduced Redis as a dependency. We probably need to step back and not only find a way to authN with it, but probably expose a "managed" Redis backend entirely.