## What this changes
This adds a tap-injector component to the `linkerd-viz` extension which is
responsible for adding the tap service name environment variable to the Linkerd
proxy container.
If a pod does not have a Linkerd proxy, no action is taken. If tap is disabled
via annotation on the pod or the namespace, no action is taken.
This also removes the environment variable for explicitly disabling tap through
an environment variable. Tap status for a proxy is now determined only be the
presence or absence of the tap service name environment variable.
Closes#5326
## How it changes
### tap-injector
The tap-injector component determines if `LINKERD2_PROXY_TAP_SVC_NAME` should be
added to a pod's Linkerd proxy container environment. If the pod satisfies the
following, it is added:
- The pod has a Linkerd proxy container
- The pod has not already been mutated
- Tap is not disabled via annotation on the pod or the pod's namespace
### LINKERD2_PROXY_TAP_DISABLED
Now that tap is an extension of Linkerd and not a core component, it no longer
made sense to explicitly enable or disable tap through this Linkerd proxy
environment variable. The status of tap is now determined only be if the
tap-injector adds or does not add the `LINKERD2_PROXY_TAP_SVC_NAME` environment
variable.
### controller image
The tap-injector has been added to the controller image's several startup
commands which determines what it will do in the cluster.
As a follow-up, I think splitting out the `tap` and `tap-injector` commands from
the controller image into a linkerd-viz image (or something like that) makes
sense.
Signed-off-by: Kevin Leimkuhler <kevin@kleimkuhler.com>
Kevin Leimkuhler