Propagate exported Service session affinity to ServiceImport

[tpantelis]

...to align with the MCS spec. If multiple clusters export a service, the fields are merged, ie for SessionAffinity, if any exported service has ClientIP then the ServiceImport will as well; for SessionAffinityConfig, the ServiceImport will inherit the first exported non-nil SessionAffinityConfig.

Fixes #1610

[submariner-bot]

🤖 Created branch: z_pr1621/tpantelis/si_session_affinity
🚀 Full E2E won't run until the "ready-to-test" label is applied. I will add it automatically once the PR has 2 approvals, or you can add it manually.

[tpantelis]

@vthapar @skitt @aswinsuryan I wonder if we should report a conflict condition if all constituent cluster services don't specify the same SessionAffinity, ie if they don't all agree on ClientIP. Currently it doesn't really matter b/c we don't implement SessionAffinity at the clusterset service level (although Istio might). Which begs the next question, should we implement it in the core DNS plugin?

For SessionAffinityConfig, we could be smarter and take the maximum ClientIP timeout value amongst the constituent services. I don't think we need to report a conflict condition if they don't all match.

[submariner-bot]

🤖 Closed branches: [z_pr1621/tpantelis/si_session_affinity]