make notifications organization-aware

[dannykopping]

Now that the multi-org feature is complete, we need a way to allow org admins to reconfigure their notification dispatch method settings (SMTP, webhook) on an org level. Org admins do not necessarily have the ability to reconfigure coderd, and thus need to make these changes on a running coderd instance.

This depends on the outcome of the Runtime Configuration RFC.

[stirby]

@dannykopping Good candidate to move into coder/coder.

Can we replace this explanation per our discussion?

From:

e.g. member bob is in org roberts; org template admin changes the workspace deleted notification to send via webhook; bob must receive these notifications via webhook but all other orgs will use the default

To:

All resources (other than users) are owned by a single org. When a notification is triggered from a resource in Org A, the preferences from that organization will be used.

Unless this is still in decision.

[dannykopping]

Blocked waiting on the outcome of the RFC.

[dannykopping]

The RFC was partially accepted.

However, concerns have been raised about authorization and validation, which both need to be addressed in the RFC.
There is no pressing requirement for these features at this time, and so coder/coder#14624 was branched off as a trimmed down version of #14470 (the original impl proposal) to address @Emyrk's immediate needs.

In order to unblock this feature we need to address the authorization & validation questions posed in the RFC.