no issue
- Increased default mailgun retry limit to 5
- Handling retry logic closer to SDK layer gives less future manual handling
- Allowed failing request to be passed through to the caller
- To be able to handle failed requests more gracefully in the future we need all available error information to be given to the caller
- The previous method with `Promise.all` would have rejected a whole batch without providing details on each specific batch.
- Limited data returned with a failed message to batch values
- Added better error handling on mega layer
- Added new column to store failed batch info
- Added reference to mailgan error docs
- Refactored batch emailer to respond with instances of an object
- It's hard to reason about the response type of bulk mailer when multiple object types can be returned
- This gives more clarity and ability to check with `instanceof` check
