Handle server-side defaults (#12)

The ScalableTarget Resource has two fields which do not work with the existing ACK CompareResource functionality. This PR fixes this issue by adding these two fields to the ignore list for compare and then adding custom logic. 

More details discussed in [Issue #796](aws-controllers-k8s/community#796)

### Testing
- I tested that the logs were as expected at each step - before any changes; after removing the compare logic entirely; after adding the custom compare function with no changes and finally the custom compare with the new checks. 
- I also checked the logs after manually testing with the suspendedState field added to the spec.

Author: mbaijal

generator.yaml

@@ -14,6 +14,8 @@ resources:
     hooks:
         sdk_read_many_post_build_request:
           code: rm.customDescribeScalableTarget(ctx, r, input)
+        delta_pre_compare:
+          code: customSetDefaults(a, b)
     fields:
       ResourceID:
         is_name: true

pkg/resource/scalable_target/custom_delta.go

@@ -0,0 +1,41 @@
+// Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"). You may
+// not use this file except in compliance with the License. A copy of the
+// License is located at
+//
+//     http://aws.amazon.com/apache2.0/
+//
+// or in the "license" file accompanying this file. This file is distributed
+// on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+// express or implied. See the License for the specific language governing
+// permissions and limitations under the License.
+
+package scalable_target
+
+import (
+	svcapitypes "github.com/aws-controllers-k8s/applicationautoscaling-controller/apis/v1alpha1"
+)
+
+func customSetDefaults(
+	a *resource,
+	b *resource,
+) {
+	if a.ko.Spec.SuspendedState == nil && b.ko.Spec.SuspendedState != nil {
+		a.ko.Spec.SuspendedState = &svcapitypes.SuspendedState{}
+	}
+	if a.ko.Spec.SuspendedState.DynamicScalingInSuspended == nil && b.ko.Spec.SuspendedState.DynamicScalingInSuspended != nil {
+		a.ko.Spec.SuspendedState.DynamicScalingInSuspended = b.ko.Spec.SuspendedState.DynamicScalingInSuspended
+	}
+	if a.ko.Spec.SuspendedState.DynamicScalingOutSuspended == nil && b.ko.Spec.SuspendedState.DynamicScalingOutSuspended != nil {
+		a.ko.Spec.SuspendedState.DynamicScalingOutSuspended = b.ko.Spec.SuspendedState.DynamicScalingOutSuspended
+	}
+	if a.ko.Spec.SuspendedState.ScheduledScalingSuspended == nil && b.ko.Spec.SuspendedState.ScheduledScalingSuspended != nil {
+		a.ko.Spec.SuspendedState.ScheduledScalingSuspended = b.ko.Spec.SuspendedState.ScheduledScalingSuspended
+	}
+
+	if a.ko.Spec.RoleARN == nil && b.ko.Spec.RoleARN != nil {
+		a.ko.Spec.RoleARN = b.ko.Spec.RoleARN
+	}
+
+}