Payload format verification and content type properties handling

[andsel]

Release notes

Manage payload format indicator property, when set verify payload format.

What does this PR do?

Updates the processing of publish messages (for all QoS) to verify the payload to be encoded in UTF-8 when property payload format indicator is set. If the validation fails, return an acknowledgement message (PUBACK for QoS1 and PUBREC for QoS2, and DISCONNECT for QoS0) with an appropriate return code.
Manage also content_type property.

Why is it important/What is the impact to the user?

Implement payload format indicator and content_typeproperty for MQTT5.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• I have added tests that prove my fix is effective or that my feature works
• I have updated the Changelog if it's a feature or a fix that has to be reported

Related issues

• Relates Payload format and content type #825