ReferenceGrant events should trigger Gateway events

[mlavacca]

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Problem Statement

Since #2774 introduced the gateway status related to TLS secret ResolvedRefs, every time a gateway event is triggered, the listener status is enriched with a new condition related to the eligibility for the gateway to reference a certain secret as a source for certificates. This condition ResolvedRef checks that either:

• the referenced secret Is in the same gateway's namespace
• a ReferenceGrant that allows that reference exists in the secret namespace

If one of these conditions is satisfied, the ResolvedRefs condition is set to true, otherwise false.

A problem occurs when:

• The Gateway is created but no ReferenceGrant exists: once the ReferenceGrant is created, the Gateway status must be updated accordingly.
• The ReferenceGrant is deleted: the Gateway status must be updated accordingly.

Proposed Solution

The Gateway controller should watch the ReferenceGrant objects and trigger a reconciliation loop for all the gateways possibly involved.

Additional information

This issue should be fixed after #2785, after which the listener status will be enforced upon every Gateway reconciliation loop, no matter if the Gateway is ready.

Acceptance Criteria

• The Gateway is created or updated but no ReferenceGrant exists: the ResolvedRef condition of the listener status must be set to false
• The Gateway is created or updated and the ReferenceGrant exists: the ResolvedRef condition of the listener status must be set to true
• The ReferenceGrant enabling a Reference is created: the corresponding Listener status is updated
• The ReferenceGrant enabling a Reference is deleted: the corresponding Listener status is updated