Create message Pact docs

[JP-Ellis]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Description

To add a new section to the docs documenting how Pact Python can be used to verify messages, both synchronous and asynchronous.

The docs should build on top of the existing consumer and provider docs.

Motivation

To help with the adoption of message verification using Pact Python

Have you tried building it?

No response

Self-service

• I'd be willing to contribute this feature to Pact Python myself.

[polyphobus]

Is this documentation issue related to the fact, that when I'm installing current version of pact-python 3.1.0 and want to do message pact testing, then my consumer test python scripts fails already at the very beginning with the import:
from pact import MessageConsumer, Provider

MessageConsumer is not found.

When downgrading to version 2.3.3 then this script works. How to do this with latest 3.x versions of pact-python?

[JP-Ellis]

Version 3 of Pact Python no longer has a dedicated MessageConsumer, since a consumer could consume a number of different kinds of interactions.

Instead, you specify that a specific interaction is asynchronous (i.e., a message) when calling upon_receiving. This returns an instance of an AsyncMessageInteraction which allows you to further configure the interaction.

I will eventually get around to writing more thorough documentation, I just haven't had the time yet 😅 Hopefully this is enough to get started though!