Customize Message timeout and retry policy.

[myhajloKo]

Hello,

I am trying to implement IPC between Device and Cloud using Azure IoT SDK C and MQTT transport protocol. From this point I need to control message retry interval a message timeout (impact on OPTION_MESSAGE_TIMEOUT, RESEND_TIMEOUT_VALUE_MIN and TELEMETRY_MSG_TIMEOUT_MIN values). According to above could you please answer for the next questions:
• Is there any limitation about minimal timeout values (for keep server side stable)?
• As I see that MQTT QoS in publishTelemetryMsg is set to DELIVER_AT_LEAST_ONCE. Does the MQTT client resent the message itself (without command from IOTHUB_CLIENT_CORE_LL_HANDLE)?
• If we will use modified the LTS version of azure-iot-sdk-c can we have support from Microsoft side in case when we faced with some bugs?

@ewertons Could you please help me with these questions?

Thank you!