feat: Introduce activationThreshold/minMetricValue for Cassandra Scaler

Signed-off-by: Jorge Turrado <jorge_turrado@hotmail.es>

content/docs/2.8/scalers/cassandra.md

@@ -23,6 +23,7 @@ triggers:
       keyspace: "test_keyspace"
       query: "SELECT COUNT(*) FROM test_keyspace.test_table;"
       targetQueryValue: "1"
+      activationTargetQueryValue: "10"
       metricName: "test_keyspace"
 ```
 
@@ -36,6 +37,7 @@ triggers:
 - `keyspace` - The name of the keyspace used in Cassandra.
 - `query` - A Cassandra query that should return single numeric value.
 - `targetQueryValue` - The threshold value that is provided by the user and used as `targetValue` or `targetAverageValue` (depending on the trigger metric type) in the Horizontal Pod Autoscaler (HPA).
+- `activationTargetQueryValue` - Target value for activating the scaler. Learn more about activation [here](./../concepts/scaling-deployments.md#activating-and-scaling-thresholds).(Default: `0`, Optional)
 - `metricName` - Name to assign to the metric. (Default: `s<X>-cassandra-<KEYSPACE>`, Optional, In case of `metricName` is specified, it will be used to generate the `metricName` like this: `s<X>-cassandra-<METRICNAME>`, where `<X>` is the index of the trigger in a ScaledObject)
 
 ### Authentication Parameters