Add LocalStack for AWS license requirement (#53)

* Add LocalStack for AWS license requirement to prerequisites

* Hyperlink LOCALSTACK_AUTH_TOKEN and clean up localstack CLI prerequisite

* Add auth token guard to start target

Author: HarshCasper

Makefile

@@ -56,6 +56,7 @@ test:
 ## Start LocalStack
 start:
 	@echo "Starting LocalStack..."
+	@test -n "${LOCALSTACK_AUTH_TOKEN}" || (echo "LOCALSTACK_AUTH_TOKEN is not set. Find your token at https://app.localstack.cloud/workspace/auth-token"; exit 1)
 	@LOCALSTACK_AUTH_TOKEN=$(LOCALSTACK_AUTH_TOKEN) localstack start -d
 	@echo "LocalStack started successfully."
 

README.md

@@ -33,7 +33,8 @@ The following diagram shows the architecture that this sample application builds
 
 ## Prerequisites
 
-- [`localstack` CLI](https://docs.localstack.cloud/getting-started/installation/#localstack-cli) with a [`LOCALSTACK_AUTH_TOKEN`](https://docs.localstack.cloud/getting-started/auth-token/).
+- A valid [LocalStack for AWS license](https://localstack.cloud/pricing). Your license provides a [`LOCALSTACK_AUTH_TOKEN`](https://docs.localstack.cloud/getting-started/auth-token/) to activate LocalStack.
+- [`localstack` CLI](https://docs.localstack.cloud/getting-started/installation/#localstack-cli).
 - [AWS CLI](https://docs.localstack.cloud/user-guide/integrations/aws-cli/) with the [`awslocal` wrapper](https://docs.localstack.cloud/user-guide/integrations/aws-cli/#localstack-aws-cli-awslocal).
 - [Python 3.11](https://www.python.org/downloads/) (same version as the Lambda runtime)
 - [`make`](https://www.gnu.org/software/make/) (**optional**, but recommended for running the sample application)