feat(makefile): allow configuring Kind cluster name for e2e tests

Introduce the `KIND_CLUSTER_NAME` variable to allow running e2e tests
on Kind clusters with custom names. The Makefile now checks for an
active cluster using the configured `KIND_CLUSTER_NAME` instead of
assuming the default 'kind'. This improves flexibility for users running
multiple Kind clusters.

Author: kersten

docs/book/src/cronjob-tutorial/testdata/project/Makefile

@@ -69,13 +69,14 @@ test: manifests generate fmt vet setup-envtest ## Run tests.
 # The default setup assumes Kind is pre-installed and builds/loads the Manager Docker image locally.
 # CertManager is installed by default; skip with:
 # - CERT_MANAGER_INSTALL_SKIP=true
+KIND_CLUSTER_NAME ?= kind
 .PHONY: test-e2e
 test-e2e: manifests generate fmt vet ## Run the e2e tests. Expected an isolated environment using Kind.
 	@command -v kind >/dev/null 2>&1 || { \
 		echo "Kind is not installed. Please install Kind manually."; \
 		exit 1; \
 	}
-	@kind get clusters | grep -q 'kind' || { \
+	@kind get clusters | grep -q '$(KIND_CLUSTER_NAME)' || { \
 		echo "No Kind cluster is running. Please start a Kind cluster before running the e2e tests."; \
 		exit 1; \
 	}

docs/book/src/getting-started/testdata/project/Makefile

@@ -65,13 +65,14 @@ test: manifests generate fmt vet setup-envtest ## Run tests.
 # The default setup assumes Kind is pre-installed and builds/loads the Manager Docker image locally.
 # CertManager is installed by default; skip with:
 # - CERT_MANAGER_INSTALL_SKIP=true
+KIND_CLUSTER_NAME ?= kind
 .PHONY: test-e2e
 test-e2e: manifests generate fmt vet ## Run the e2e tests. Expected an isolated environment using Kind.
 	@command -v kind >/dev/null 2>&1 || { \
 		echo "Kind is not installed. Please install Kind manually."; \
 		exit 1; \
 	}
-	@kind get clusters | grep -q 'kind' || { \
+	@kind get clusters | grep -q '$(KIND_CLUSTER_NAME)' || { \
 		echo "No Kind cluster is running. Please start a Kind cluster before running the e2e tests."; \
 		exit 1; \
 	}

docs/book/src/multiversion-tutorial/testdata/project/Makefile

@@ -69,13 +69,14 @@ test: manifests generate fmt vet setup-envtest ## Run tests.
 # The default setup assumes Kind is pre-installed and builds/loads the Manager Docker image locally.
 # CertManager is installed by default; skip with:
 # - CERT_MANAGER_INSTALL_SKIP=true
+KIND_CLUSTER_NAME ?= kind
 .PHONY: test-e2e
 test-e2e: manifests generate fmt vet ## Run the e2e tests. Expected an isolated environment using Kind.
 	@command -v kind >/dev/null 2>&1 || { \
 		echo "Kind is not installed. Please install Kind manually."; \
 		exit 1; \
 	}
-	@kind get clusters | grep -q 'kind' || { \
+	@kind get clusters | grep -q '$(KIND_CLUSTER_NAME)' || { \
 		echo "No Kind cluster is running. Please start a Kind cluster before running the e2e tests."; \
 		exit 1; \
 	}

pkg/plugins/golang/v4/scaffolds/internal/templates/makefile.go

@@ -144,13 +144,14 @@ test: manifests generate fmt vet setup-envtest ## Run tests.
 # The default setup assumes Kind is pre-installed and builds/loads the Manager Docker image locally.
 # CertManager is installed by default; skip with:
 # - CERT_MANAGER_INSTALL_SKIP=true
+KIND_CLUSTER_NAME ?= kind
 .PHONY: test-e2e
 test-e2e: manifests generate fmt vet ## Run the e2e tests. Expected an isolated environment using Kind.
 	@command -v kind >/dev/null 2>&1 || { \
 		echo "Kind is not installed. Please install Kind manually."; \
 		exit 1; \
 	}
-	@kind get clusters | grep -q 'kind' || { \
+	@kind get clusters | grep -q '$(KIND_CLUSTER_NAME)' || { \
 		echo "No Kind cluster is running. Please start a Kind cluster before running the e2e tests."; \
 		exit 1; \
 	}

testdata/project-v4-multigroup/Makefile

@@ -65,13 +65,14 @@ test: manifests generate fmt vet setup-envtest ## Run tests.
 # The default setup assumes Kind is pre-installed and builds/loads the Manager Docker image locally.
 # CertManager is installed by default; skip with:
 # - CERT_MANAGER_INSTALL_SKIP=true
+KIND_CLUSTER_NAME ?= kind
 .PHONY: test-e2e
 test-e2e: manifests generate fmt vet ## Run the e2e tests. Expected an isolated environment using Kind.
 	@command -v kind >/dev/null 2>&1 || { \
 		echo "Kind is not installed. Please install Kind manually."; \
 		exit 1; \
 	}
-	@kind get clusters | grep -q 'kind' || { \
+	@kind get clusters | grep -q '$(KIND_CLUSTER_NAME)' || { \
 		echo "No Kind cluster is running. Please start a Kind cluster before running the e2e tests."; \
 		exit 1; \
 	}

testdata/project-v4-with-plugins/Makefile

@@ -65,13 +65,14 @@ test: manifests generate fmt vet setup-envtest ## Run tests.
 # The default setup assumes Kind is pre-installed and builds/loads the Manager Docker image locally.
 # CertManager is installed by default; skip with:
 # - CERT_MANAGER_INSTALL_SKIP=true
+KIND_CLUSTER_NAME ?= kind
 .PHONY: test-e2e
 test-e2e: manifests generate fmt vet ## Run the e2e tests. Expected an isolated environment using Kind.
 	@command -v kind >/dev/null 2>&1 || { \
 		echo "Kind is not installed. Please install Kind manually."; \
 		exit 1; \
 	}
-	@kind get clusters | grep -q 'kind' || { \
+	@kind get clusters | grep -q '$(KIND_CLUSTER_NAME)' || { \
 		echo "No Kind cluster is running. Please start a Kind cluster before running the e2e tests."; \
 		exit 1; \
 	}

testdata/project-v4/Makefile

@@ -65,13 +65,14 @@ test: manifests generate fmt vet setup-envtest ## Run tests.
 # The default setup assumes Kind is pre-installed and builds/loads the Manager Docker image locally.
 # CertManager is installed by default; skip with:
 # - CERT_MANAGER_INSTALL_SKIP=true
+KIND_CLUSTER_NAME ?= kind
 .PHONY: test-e2e
 test-e2e: manifests generate fmt vet ## Run the e2e tests. Expected an isolated environment using Kind.
 	@command -v kind >/dev/null 2>&1 || { \
 		echo "Kind is not installed. Please install Kind manually."; \
 		exit 1; \
 	}
-	@kind get clusters | grep -q 'kind' || { \
+	@kind get clusters | grep -q '$(KIND_CLUSTER_NAME)' || { \
 		echo "No Kind cluster is running. Please start a Kind cluster before running the e2e tests."; \
 		exit 1; \
 	}