workflow-service@v0.6.529-dev-4b62004e3: feat(webhooks): enhance webhook subscription handling (#2933)

* feat(webhooks): enhance webhook subscription handling

- Update SubscriptionSchema to support 'email' alongside 'webhook'
- Implement mergeSubscriptions function to handle subscription merging
- Introduce unit tests for mergeSubscriptions functionality

(your webhook subscriptions are now better organized than your last family reunion)

* refactor(webhooks): simplify getWebhooks function parameters

- Change getWebhooks function to accept a single object argument
- Update calls to getWebhooks throughout the workflow classes with new syntax

(If clarity were currency, your parameter names would be penny stocks)