Add max connections configuration to GatewayClassConfig CRD

[nathancoleman]

Changes proposed in this PR:

Add a new field to our GatewayClassConfig CRD that is piped down to the ingress-gateway config entry for overriding the default connection maximum in Envoy (1,024)

How I've tested this PR:

Create new Gateways with and without this setting in the GatewayClassConfig. For each Gateway, check the corresponding ingress-gateway config entry in Consul for the proper override.

Example

$ kubectl get gatewayclassconfig consul-api-gateway -o yaml | yq .spec.connectionManagement
maxConnections: 4096

$ consul config read -kind ingress-gateway -name api-gateway
{
    "Kind": "ingress-gateway",
    "Name": "api-gateway",
    "TLS": {
        "Enabled": false
    },
    "Listeners": null,
    "Meta": {
        "consul-api-gateway/k8s/Gateway.Name": "api-gateway",
        "consul-api-gateway/k8s/Gateway.Namespace": "consul",
        "external-source": "consul-api-gateway"
    },
    "Defaults": {
        "MaxConnections": 4096,
        "MaxPendingRequests": 0,
        "MaxConcurrentRequests": 0
    },
    "CreateIndex": 42,
    "ModifyIndex": 42
}

How I expect reviewers to test this PR:

See above

Checklist:

• Tests added
• CHANGELOG entry added

  Run make changelog-entry for guidance in authoring a changelog entry, and
  commit the resulting file, which should have a name matching your PR number.
  Entries should use imperative present tense (e.g. Add support for...)

[nathancoleman]

Personal review

[nathancoleman]

connectionManagement.maxConnections is somewhat long; however, I opted not to abbreviate to something like connMgmt.maxConns since we haven't abbreviated any other parts of the spec.

[nathancoleman]

The ResolvedGateway is what we have access to when deriving the ingress-gateway config entry that we're sending to Consul, so it needs to be aware of any config that we depend on there. This is internal, so it can evolve in the future if we wind up having other connection management config values to pipe through.

[nathancoleman]

Exported this so that the JSON marshaler includes it when we serialize for writing to the store backend.

If not exported, we don't have any idea what the max connections value is when rehydrating from the store and syncing into Consul, which we do at an interval in the background for resiliency.

[sarahalsmiller]

Looks good to me, appreciate your clarifying comments as always