* Changes remote exec KV read to call GetTokenForAgent(), which can use
the acl_agent_token instead of the acl_token.
Fixes#3160.
* Fixes remote exec unit test with ACLs.
* Adds unhappy ACL path to unit tests for remote exec.
* Obfuscates ACL tokens appearing in /v1/acl APIs.
* Makes test positively identify the desired strings.
* Adds an example and explanation of the regular expression.
Cancellation channels are often derived from a Context, which
returns a directional `<-chan struct{}` from Done(). In order to use
this with parts of of the consul API, one is required to create a new
channel and dispatch a separate goroutine to watch for context
cancellation and close the new channel.
Changing the signature for the methods that take cancellation channels
will allow easier integration with existing uses of Context. Since the
cancellation pattern only reads from these channels, there should be no
backwards incompatibility with existing codebases, and most of the
methods already accept only the correct type.
* Moves magic check and service constants into shared structs package.
* Removes the "consul" service from local state.
Since this service is added by the leader, it doesn't really make sense to
also keep it in local state (which requires special ACLs to configure), and
requires a bunch of special cases in the local state logic. This requires
fewer special cases and makes ACL bootstrapping cleaner.
* Makes coordinate update ACL log message a warning, similar to other AE warnings.
* Adds much more detailed examples for bootstrapping ACLs.
This can hopefully replace https://gist.github.com/slackpad/d89ce0e1cc0802c3c4f2d84932fa3234.
