Modify natss channel to use CRD

[akashrv]

Refer to decision made in #1002
This feature request is to update in-memory channel

[akashrv]

/milestone v0.7.0

[vaikas]

This should also move to messaging.knative.dev as part of that work as per.
https://github.com/knative/eventing/blob/master/docs/decisions/eventing-and-messaging.md

[nachocano]

grabbing this one as nobody has
/assign

[nachocano]

We need the following that will be needed for every channel CRD implementations:

• Permissions to update channels from the subscription controller. This is needed for every channel. Thanks @akashrv who found the problem while testing the Kafka CRD. In my cluster it was working as I had an old admin role. The aggregate roles might work for this [#1341]
• Have a defaulting mechanism for specifying a default channel CRD. @vaikas-google has some WIP of this in the Pipeline PR. @grantr will take a look at it in Support for default channel #1343
• Stats and controller UTs (Natss CRD Controller UT + Dispatcher Tracing #1361)
• Migration plan on how to deprecate the old provisioner model. Might end up adding a message in Status. Same as inmemory channel (Channel Deprecation Condition #1366)
• Tracing for all new dispatcher CRDs (InMemoryChannel tracing #1364, Kafka CRD Controller UT + Dispatcher tracing #1363, Natss CRD Controller UT + Dispatcher Tracing #1361)
• Update dispatcher with the new subscribers statuses (@akashrv is taking care of this)

fyi @akashrv @Harwayne

[devguyio]

@nachocano apologies for late replies, we had some internal delays and had planned to work on it for next release starting next week. Thanks for picking it up! We can test on Kyma once you have a PR if you'd like.

[nachocano]

@Abd4llA thanks Ahmed! This PR #1327 was merged yesterday night and included the changes. There is a follow up that should get in today (#1341). After that one gets in, I'll ping you to see if you can test it in Kyma!

[nachocano]

@Abd4llA #1341 is merged. Can you guys test it on Kyma, both the previous provisioner model, and the new CRD one? Note that the previous yaml is now under config/provisioner. The new ones are just under config