[Terraform] New Terraform Provider generator (#22949)

* [new] Add Terraform provider generator

Add a new experimental code generator that produces HashiCorp Terraform
providers from OpenAPI specifications using the Plugin Framework SDK.

The generator (terraform-provider) supports:
- CRUD operation detection from REST patterns and vendor extensions
- Resource, data source, and model generation per API tag
- HTTP client with API key, bearer token, and basic auth
- Type mapping from OpenAPI/Go types to Terraform schema types
- Import state support
- Configurable provider name, registry address, and version

Includes mustache templates for: provider, resources, data sources,
models, client, go.mod, GNUmakefile, README, and example configs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* [new] Add Terraform provider petstore sample and acceptance tests

Add sample generation config and generated Terraform provider for the
petstore OpenAPI spec, along with Go acceptance tests that exercise
the provider lifecycle (create, read, update, delete, import).

Generated output includes:
- Provider with auth configuration (API key, bearer, basic)
- Pet, User, and Store resources and data sources
- Client package with HTTP client and model structs
- Go acceptance tests using terraform-plugin-testing
- Example Terraform configurations for each resource/data source

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: docs

* terraform: add more sample tests and ci workflow

* ci: get ci passing

* ci: fixes

* chore: docs

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/samples-terraform.yaml

@@ -0,0 +1,46 @@
+name: Samples Terraform
+
+on:
+  push:
+    paths:
+      - 'samples/client/petstore/terraform/**'
+      - 'samples/client/petstore/terraform-addpet/**'
+      - 'samples/client/petstore/terraform-server/**'
+      - 'samples/client/others/terraform/**'
+  pull_request:
+    paths:
+      - 'samples/client/petstore/terraform/**'
+      - 'samples/client/petstore/terraform-addpet/**'
+      - 'samples/client/petstore/terraform-server/**'
+      - 'samples/client/others/terraform/**'
+
+jobs:
+  build:
+    name: Build Terraform Provider
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        sample:
+          - samples/client/petstore/terraform/
+          - samples/client/petstore/terraform-addpet/
+          - samples/client/petstore/terraform-server/
+          - samples/client/others/terraform/allof-discriminator/
+          - samples/client/others/terraform/oneof-anyof-required/
+          - samples/client/others/terraform/oneof-discriminator-lookup/
+    steps:
+      - uses: actions/checkout@v5
+      - uses: actions/setup-go@v6
+        with:
+          go-version: "stable"
+      - run: go version
+      - name: Install Dependencies
+        working-directory: ${{ matrix.sample }}
+        run: |
+          go mod tidy
+      - name: Build provider
+        working-directory: ${{ matrix.sample }}
+        run: go build -v ./...
+      - name: Run tests
+        working-directory: ${{ matrix.sample }}
+        run: go test ./... -v -timeout 120m