Fix TLS Errors on Lambda

[freiSMS]

Proposed changes

Send data before response + promisify.
Lambda environments skip async sending executions. In the next request the lambda tries to send them again. This can lead to runtime errors or missing data on the dashboard (depending on your lambda settings).

• improve hint if config is missing

fixes #837

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed