Add hooks after input request creation, but before request is submitted.

[mbaijal]

Description of changes

Adds the post_build_request hooks which are called AFTER the call to construct the Input shape but BEFORE the API operation.

Sample Use:

resources:
  ScalableTarget:
    hooks:
        sdk_read_many_post_build_request:
          code: rm.customDescribeScalableTarget(ctx, r, input)

Testing

Fixed the bug in applicationAutoscaling where one could not create a ScalableTarget resource which would throw the following error -

Reconciler error	{"controller": "scalabletarget", "request": "default/dynamodb-scalable-target-2ir12cp", "error": "ValidationException: Scalable dimension cannot be provided without resource IDs."}

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jaypipes]

Yup, nice addition, thank you @mbaijal!

[ack-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: jaypipes, mbaijal, surajkota

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment