Fixes #6042

Add new task group service hook for registering group services like
Connect-enabled services.

Does not yet support checks.

vendor: update testify to v1.4.0

This lets us turn Mirage logging on without editing any
files, which makes it easier to switch between branches.

Block rpc handling until state store is caught up

* structs: use seperate SidecarTask struct for sidecar_task stanza and add merge

* nomad: merge SidecarTask into proxy task during connect Mutate hook

link-local addresses can be fingerprinted

Adds an example job for Consul Connect integration as well as an
annotated example job.

Add a link to the discussion forum on the resources page

Added note to document that link-local addresses can be fingerprinted in
cases where no routable address can be found.  Crosslinked to
`"fingerprint.network.disallow_link_local"` because they are somewhat
related and it is documented at a reasonable distance from this setting.

docker: Fix issue where an exec may never timeout

--payload -> --data for curl; consistent @payload

syntax fix; add example for alloc exec -task

NetworkIsolation was left out of the task config when using an
external task driver plugin

* nomad: add admission controller framework

* nomad: add admission controller framework and Consul Connect hooks

* run admission controllers before checking permissions

* client: add default node meta for connect configurables

* nomad: remove validateJob func since it has been moved to admission controller

* nomad: use new TaskKind type

* client: use consts for connect sidecar image and log level

* Apply suggestions from code review
Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>

* nomad: add job register test with connect sidecar

* Update nomad/job_endpoint_hooks.go
Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>

Consul Connect must route traffic between network namespaces through a
public interface (i.e. not localhost). In order to support testing in
dev mode, users needed to manually set the interface which doesn't
make for a smooth experience.

This commit adds a facility for adding optional parameters to the
`nomad agent -dev` flag and uses it to add a `-dev=connect` flag that
binds to a public interface on the host.

NetIsolationModes and MustInitiateNetwork were left out of the
driver Capabilities when using an external task driver plugin
Signed-off-by: Lucas BEE <pouulet@gmail.com>

Add validation for kind field if it is a consul connect proxy

Ease user customizations of Makefile

Allow users to customize their makefiles by adding custom
targets/variables without checking them in.

Allow honoring `GO_TAGS` environment variable if set.  Currently, users
must set variable as a makefile argument e.g. `make GO_TAGS=ui dev`, and
this allows us to use env-var syntax (e.g. `GO_TAGS=ui make dev`) and
make it convenient to set GO_TAGS globally.

circleci: fix test reports and some refactoring

This adds the “Jump to section” feature from Terraform’s documentation.

Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>

When rendering a task template, the `plugin` function is no longer
permitted by default and will raise an error. An operator can opt-in
to permitting this function with the new `template.function_blacklist`
field in the client configuration.

When rendering a task template, path parameters for the `file`
function will be treated as relative to the task directory by
default. Relative paths or symlinks that point outside the task
directory will raise an error. An operator can opt-out of this
protection with the new `template.disable_file_sandbox` field in the
client configuration.

pulls in configuration option for blacklisting template functions from:
https://github.com/hashicorp/consul-template/pull/1243
https://github.com/hashicorp/consul-template/pull/1246

pulls in configuration option for file sandboxing from:
https://github.com/hashicorp/consul-template/pull/1249
https://github.com/hashicorp/consul-template/pull/1254

pulls in vault KVv2 read fixes from:
https://github.com/hashicorp/consul-template/pull/1253