Batch Send

[zhaparoff]

Need to implement API for https://api-docs.mailtrap.io/docs/mailtrap-api-docs/48b526aa487b1-batch-send-email-including-templates

[yanchuk]

also https://api-docs.mailtrap.io/docs/mailtrap-api-docs/c323263dc45c5-batch-send-email-including-templates and https://api-docs.mailtrap.io/docs/mailtrap-api-docs/48b526aa487b1-batch-send-email-including-templates