Bugfix/set default headers for properties in pika

[oxeye-nikolay]

Description

The pika instrumentation injects the context into the properties.headers of the connection. If the properties are not provided, it generates a new BasicProperties object, which by default sets headers to None instead of an empty dict - which results in a failure to inject the context into the headers.
The fix was to set the headers={} by default when creating the BasicProperties object.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

A pika client that creates a pika connection and executes basic_publish without properties.

Does This PR Require a Core Repo Change?

• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added

[owais]

shoudl this be producer/consumer instead of client/server?

[oxeye-nikolay]

I guess you're right as pika does use callbacks. Updated.

[owais]

It is more about the communication being a single round-trip like HTTP vs async message queue one like RabbitMQ. I'm guessing pika enables the later type of communication, right?

[oxeye-nikolay]

Yeah, You create a single connection and declare one or many channels, over which you declare one or many callbacks. So it is more of a producer/consumer than client/server.