Send data to ServiceClients only if present

[nikhilym]

Description

This PR includes changes to the default API client class, so that the raw data is sent to the Alexa service clients only if the request.body is not null. Without that, requests library calls leads to incorrect content type for responses, as mentioned in #38 .

The PR also includes scoping requests library to <= 2.19.1, which scopes urllib3 < 1.24, without which the standard and dynamo package installations might fail. This can be checked from the build failure of docs here

Motivation and Context

#38

Testing

Ran sdk tests using scripts/ci/run_tests

Screenshots (if appropriate)

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 read the README document
• I have added tests to cover my changes
• All new and existing tests passed

License

• By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.