chore(*) add tidy target for go mod maintenance

Signed-off-by: Nikolay Nikolaev <nikolay.nikolaev@konghq.com>

Makefile

@@ -226,13 +226,22 @@ vet: ## Dev: Run go vet
 	@# for consistency with `fmt`
 	make vet -C pkg/plugins/resources/k8s/native
 
+.PHONY: tidy
+tidy:
+	@for m in . ./api ./pkg/plugins/resources/k8s/native; do \
+		pushd $$m ; \
+		rm go.sum ; \
+		go mod tidy ; \
+		popd; \
+	done
+
 golangci-lint: ## Dev: Runs golangci-lint linter
 	$(GOLANGCI_LINT_DIR)/golangci-lint run -v
 
 imports: ## Dev: Runs goimports in order to organize imports
 	goimports -w -local github.com/Kong/kuma -d `find . -type f -name '*.go' -not -name '*.pb.go' -not -path './vendor/*'`
 
-check: generate fmt vet docs golangci-lint imports ## Dev: Run code checks (go fmt, go vet, ...)
+check: generate fmt vet docs golangci-lint imports tidy ## Dev: Run code checks (go fmt, go vet, ...)
 	make generate manifests -C pkg/plugins/resources/k8s/native
 	git diff --quiet || test $$(git diff --name-only | grep -v -e 'go.mod$$' -e 'go.sum$$' | wc -l) -eq 0 || ( echo "The following changes (result of code generators and code checks) have been detected:" && git --no-pager diff && false ) # fail if Git working tree is dirty