Add runbook to analyze vpc flow logs

runbooks/source/analyze-vpc-flow-logs.html.md.erb

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+---
+title: Analyze VPC Flow Logs
+weight: 219
+last_reviewed_on: 2023-12-14
+review_in: 6 months
+---
+
+# <%= current_page.data.title %> 
+
+Cloud Platform `live-1` VPC is connected to various other MoJ AWS accounts VPC using Transit Gateway. In order to debug network connectivity issues 
+that are coming to/from Cloud Platform VPC, the VPC flow logs are enabled. These logs are stored in an S3 bucket and can be analyzed using Athena when needed.
+
+The steps involve a pointy-clicky exercise to generate Athena integration by creating a CloudFormation stack using a template and use that as a datasource in Athena
+Follow the steps as mentioned in the blog: [AWS blog - Analyze VPC Flow Logs with point-and-click Amazon Athena integration](https://aws.amazon.com/blogs/networking-and-content-delivery/analyze-vpc-flow-logs-with-point-and-click-amazon-athena-integration/).
+
+Things to note:
+- When creating a CloudFormation template, use the `Partition: Daily` option. This will create a partition for each day and will make it easier to query the logs for a specific day.
+- Provide Partition start date and end date closer when the issue was observed. The duration is limited to 20 days
+- Create two s3 buckets one for CloudFormation template and and another one to store the Athena query results which you will provide when creating the CloudFormation stack.
+- When the flow logs are downloaded and the user has investigated the issue, delete the created s3 buckets for CloudFormation template and Athena query results and the CloudFormation stack.
+
+