DPC-5102 Handle error in generate token github action (#2874)

## 🎫 Ticket

https://jira.cms.gov/browse/DPC-5102

## 🛠 Changes

Github Action Workflow for generating token validates token before
loading into parameter store

## ℹ️ Context

We ran this workflow when the API was down, and an html page was entered
as the golden macaroon, which made everything else fail.

## 🧪 Validation

- Ran the workflow with api up and verified golden macaroon in dev
parameter store changed:
https://github.com/CMSgov/dpc-app/actions/runs/20664928982
- Ran the workflow with api down and verified the workflow failed and
that the token was not updated:
https://github.com/CMSgov/dpc-app/actions/runs/20665012110

Author: jdettmannnava

.github/workflows/generate-macaroon.yml

@@ -44,6 +44,8 @@ jobs:
       - name: Get and load Golden Macaroon
         run: |
           ALB_URL=$(aws elbv2 describe-load-balancers --names dpc-${{ inputs.env }}-frontend-internal | jq -r '.LoadBalancers[0].DNSName')
-          token=$(curl -X POST ${ALB_URL}:9900/tasks/generate-token)
-          aws ssm put-parameter --name '/dpc/${{ inputs.env }}/web/golden_macaroon' --type 'SecureString' --value "${token}" --key-id 'alias/dpc-${{ inputs.env }}-master-key' --overwrite
-          
+          token=$(curl --fail --silent -X POST ${ALB_URL}:9900/tasks/generate-token)
+          if [[ -n $token ]]; then
+             echo $token | base64 -d -i 1>/dev/null && \
+                 aws ssm put-parameter --name '/dpc/${{ inputs.env }}/web/golden_macaroon' --type 'SecureString' --value "${token}" --key-id 'alias/dpc-${{ inputs.env }}-master-key' --overwrite
+          fi