Expose KEDA ScaledObject and HTTP scaling configuration options

[aliok]

Problem

Several KEDA scaling configuration values are currently hardcoded and not configurable via func.yaml.

ScaledObject (Kafka trigger)

Hardcoded in pkg/keda/kafka_scaling.go:

• cooldownPeriod: 300 (seconds) — how long before scaling down after triggers go idle
• pollingInterval: not set, defaults to 30 seconds — how often KEDA checks metrics

Not exposed from KEDA's Kafka scaler:

• offsetResetPolicy
• allowIdleConsumers
• excludePersistentLag
• scaleToZeroOnInvalidOffset
• limitToPartitionsWithLag

HTTPScaledObject (HTTP trigger)

Hardcoded in pkg/keda/deployer.go:

• CooldownPeriod: 300
• ScalingMetric.Rate.TargetValue: 100 (requests/sec)
• ScalingMetric.Rate.Window: 1 minute
• ScalingMetric.Rate.Granularity: 1 second

Proposed solution

Add optional fields to scale.keda in func.yaml for the common options:

deploy:
  options:
    scale:
      keda:
        pollingInterval: 15
        cooldownPeriod: 60
        triggers:
          - type: kafka
            lagThreshold: 5
          - type: http
            targetValue: 50

Start with pollingInterval, cooldownPeriod, and HTTP targetValue as the most impactful. The Kafka-specific options (allowIdleConsumers, etc.) can be added later as needed.