Create a monitoring-alerting-samples

This repository was really helpful for me to backup and restore Cloud Monitoring dashboards.

I'd like to have a similar repository for sharing alerting policies, following the same structure.

I already adapted the script (i.e., like alerting.sh) and tested it for AI/ML alert policies.

```bash
#!/usr/bin/env bash

set -eE

ACTION=${1:?"action [import | export ] is required as argument \$1"}

alerting_export () {
# action is $1
alert_id=${2:?"alert id is required as argument \$2"}
project_id=${3:?"project id is required as argument \$3"}
output_file=${4:?"output file name is requred as argument \$4"}

project_number=$(gcloud projects describe "${project_id}" --format="value(projectNumber)")

echo "Exporting alerting \"$alert_id\" from project \"$project_id\" to file \"${output_file}\""

gcloud alpha monitoring policies describe \
"projects/${project_number}/alertPolicies/${alert_id}" --format=json \
| jq 'del(.name, .creationRecord, .mutationRecord, .notificationChannels)' \
| jq 'del(.conditions[].name)' \
> "${output_file}"

echo "Export finished"
}

alerting_import () {
# action is $1
project_id=${2:?"project id is required as argument \$2"}
input_file=${3:?"input file is requred as argument \$3"}

gcloud alpha monitoring policies create \
--project "${project_id}" \
--policy-from-file "${input_file}"
}

if [ "$ACTION" = "export" ]; then
alerting_export "$@"
elif [ "$ACTION" = "import" ]; then
alerting_import "$@"
else
echo "unknown action: ${ACTION}"
exit 1
fi
```

**Note: this script doesn't export and create notification channels**.