Refactor addBackendPolicyIfConfigured to allow future features

[sawsa307]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
Refactor IR in GCE to allow additional features.

Which issue(s) this PR fixes:

Does this PR introduce a user-facing change?:

None

[spencerhance]

Thanks @sawsa307!

[spencerhance]

Nit: how do we usually handle invalid config? Could we add a log here if the backendConfig had affinityCookieTtlSec set without affinityType of GENERATED_COOKIE?

[sawsa307]

Sounds good! Created a function to check backend config before processing translation.

[spencerhance]

official /lgtm /approve

(although I don't have OWNERS approval)

[sawsa307]

/assign @spencerhance
/assign @LiorLieberman

[robscott]

Thanks @sawsa307! Will defer to @LiorLieberman for final approval.

/lgtm

[LiorLieberman]

/lgtm
/approve

Thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: LiorLieberman, sawsa307, spencerhance

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [LiorLieberman]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment