Add support for Sweego transactional email API

[pydubreucq]

Hi,
I'm reaching out to see if you'd be interested in adding support for Sweego, a transactional email service provider based in France.
To help you evaluate this addition, here's a breakdown of how Sweego's API aligns with Anymail's feature set:

Core Email Features

• HTML and text bodies: Both supported
• Attachments: Standard attachments with base64 encoding
• Inline images: Supported via Content-ID references
• Extra headers: Custom headers can be added
• Multiple recipients: To, Cc, Bcc supported
• Reply-To: Supported

ESP-specific Features

• Tags: Supported for categorization and filtering
• Metadata: Custom key-value pairs per message
• Click and open tracking: Can be enabled/disabled per message
• Message ID: Returned in API response for tracking

Advanced Features

• Webhooks: Event notifications for delivery status, opens, clicks, bounces, complaints, etc.
• Template support: Server-side template rendering with merge variables
• Batch sending: Bulk operations with per-recipient personalization
• Inbound email: Can receive emails via webhook (MX records pointing to Sweego)

API Characteristics

• Authentication: API key
• API URL: https://api.sweego.io/
• Request format: JSON
• Response format: JSON with message ID
• Documentation: https://learn.sweego.io/

I'd be happy to submit a PR if you're open to adding Sweego support.
I'm available to answer any questions about Sweego's API specifics.

Thanks for maintaining this excellent package and your answer :)

[medmunds]

@pydubreucq thanks for the detailed feature breakdown. Yes, Sweego looks like a great fit for Anymail. The one other requirement is that we're able to run regular integration tests against the live API, and it looks like Sweego's free tier with 100 sends/day would handle that easily.

A PR would be welcome.

People can express interest in this by adding a thumbs-up reaction to the top comment above.