[AMQP] Release v2.0.0

Please see https://github.com/cloudevents/sdk-go/releases/tag/v2.0.0 for details.

Introduce Sub-modules

We have broken the protocols up into go sub-modules, this is a dependency breaking change in only that integrators will need to import additional modules for protocols outside of gochan and http.

This is looking like the final RC and if this goes well we will cut 2.0.0 from this RC5 tag.

Thanks!

[WIP] Attempting to understand go mod versioning of submodules

testing, sorry for noise

[WIP] testing submodules for kakfa.

Please ignore for now.

Fixed important data race and performance regression

• Removed perf regression on format.Lookup: #503
• Cleaned up all data races in sdk: #502

Cleaning http error codes and Kafka improvements.

• Removed v1 directory, please use the v1 releases, via go mod.
• Bug fixes for Kakfa consumer groups.
• New Kafka Samples.
• All samples documented.
• Client polling now has parallelism.
• Status codes now flow properly for reply cases.
• Bug fixes around return codes in HTTP protocol.
• Targeting end of May for a final v2.0.0 release.

Release Candidate 2, lifecycle fixes, pubsub improvements

We have found and fixed a few lifecycle issues related to message.Finish.
Pub/Sub has bug fixes and retries are now added.
Cucumber tests have been added from the cloudevents/conformance repo.

Before we can call a 2.0.0, we will be taking a look at conformance to the webhook spec, there are some missing OPTION interactions that are blocking the final v2 release.

Fixing tracing.

Update with bugfixes for v1, released off release-1.y.z branch.

Release Candidate 1

I'm pleased to announce that the first release candidate of v2 is out! We're not far from delivering to you the new version of official CloudEvents sdk-go v2.

Among several fixes, we have a bunch of important changes from preview8:

• HTTP now has support for retrying requests (#436, #442). You can use it decorating the Send and Request context using helpers in context module
• Redesigned transformers to be easier to use and more performant (#446)

We are also working on improving our codebase with performance tweaks (#444) and linting (#435, #432)

Thanks to all contributors that are actively participating to this project and made this release possible.

Added protocol.Result and reworked Event.SetData/Event.Data

This release includes two new important changes:

• Adding protocol.Result to Send and Request client interface (#425): Now you can use cloudevents.IsACK(result)/cloudevents.isNACK to test the result of Client.Send() and Client.Request()
• Reworking datacodec package (#428): Now in v0.3 and v1.0 the Data field is consistent and Event.SetData()/Event.Data() and datacodec now are decoupled from base64 encoding/decoding

Also included two crucial fixes:

• Fix a race condition in the distributed tracing unit tests (#420)
• Fixed ResponseWriter. Now it really writes the content-length, only when possible (best effort) (#424)