Feat: Adds DCR Provider resource support

[rspurgeon]

Summary

Add first-class DCR provider support across kongctl.

What changed

• added declarative dcr_providers resource support in the loader, planner, executor, state client, and protection lookup paths
• added imperative get and list support for DCR providers with Konnect-first aliases:
  • kongctl get dcr-providers
  • kongctl get dcr-provider <id|name>
  • kongctl list dcr-providers
• added adopt dcr-provider support
• added declarative dump support for --resources=dcr_providers
• added standalone declarative DCR provider examples under docs/examples/declarative/dcr-providers
• added focused unit coverage for DCR planner/resource/executor behavior
• added an end-to-end DCR provider workflow scenario covering:
  • plan
  • apply
  • sync
  • delete
  • dump
  • adopt
  • get
  • list

Implementation notes

• DCR provider CRUD/listing uses the existing sdk-konnect-go client configuration, with a raw HTTP helper path where the generated SDK response union decoding is not reliable for Konnect DCR responses.
• DCR issuer values are normalized on write/comparison to avoid trailing-slash plan noise.
• DCR update execution now constructs typed SDK config unions explicitly so provider-specific config updates are applied correctly.
• Azure DCR examples document the issuer nuance observed during testing.

Validation

• not run in this publish step

Closes #32

[Copilot]

Pull request overview

Copilot reviewed 57 out of 57 changed files in this pull request and generated 3 comments.