Add Go types for DataflowJob to direct controller

[justinsb]

As part of moving resources from terraform controllers to direct controllers (Epic #5954), we need to create the Go types for DataflowJob.

Currently, DataflowJob is managed by the Terraform controller (marked with tf2crd=true). The goal is to create the Go types in apis/dataflow/v1beta1/ so that we can eventually migrate the controller implementation to the "direct" approach.

Instructions

1. Add to generate.sh:
   Modify apis/dataflow/v1beta1/generate.sh to include DataflowJob.
   It likely maps to google.dataflow.v1beta3.Job.
   Example:

   go run . generate-types \
     --service google.dataflow.v1beta3 \
     --api-version dataflow.cnrm.cloud.google.com/v1beta1 \
     --resource DataflowFlexTemplateJob:FlexTemplateRuntimeEnvironment \
     --resource DataflowJob:Job

2. Generate Scaffolding:
   Run apis/dataflow/v1beta1/generate.sh. This should create apis/dataflow/v1beta1/dataflowjob_types.go.

3. Iterate on Types:
   Compare the generated CRD with the existing one using dev/tasks/diff-crds.
   Modify apis/dataflow/v1beta1/dataflowjob_types.go until the CRD matches the existing one at config/crds/resources/apiextensions.k8s.io_v1_customresourcedefinition_dataflowjobs.dataflow.cnrm.cloud.google.com.yaml.

   Acceptance Criteria:

   • Running dev/tasks/diff-crds should not show differences (or minimal acceptable ones like descriptions).
   • Changes to the schema (fields added/removed) are NOT acceptable.

4. Copyright Headers:
   Ensure the new file has the correct copyright header:

   // Copyright 2026 Google LLC

5. Labels:
   Ensure the controller-runtime annotations match the existing CRD labels, including:

   // +kubebuilder:metadata:labels="cnrm.cloud.google.com/managed-by-kcc=true"
   // +kubebuilder:metadata:labels="cnrm.cloud.google.com/system=true"
   // +kubebuilder:metadata:labels="cnrm.cloud.google.com/stability-level=stable"
   // +kubebuilder:metadata:labels="cnrm.cloud.google.com/tf2crd=true"

6. Status:
   status.observedGeneration should be an int64.

This issue is part of Epic #5954.