Updated the `IEmailService` interface and related components to
support multiple recipients in the `SendEmailAsync` method.
- Replaced `Recipient` with `Recipients` in `SendEmailCommand`,
`OutgoingEmailEvent`, and `EmailsController`.
- Updated `SendEmailCommandValidator` to validate a collection
of recipients, ensuring at least one valid email address.
- Modified `LimilabsEmailService` to handle multiple recipients
by iterating over the collection and adding each to the email.
- Adjusted `OutgoingEmailConsumer` to process and log multiple
recipients.
- Updated logging and response structures to reflect the changes.
These changes enable the system to handle emails with multiple
recipients while maintaining proper validation and logging.