Allow for custom uid/gid for consul user

[nferch]

The uid and gid generated in the container build process is likely to conflict with other services and containers, which is operationally inconvenient and could lead to security issues.

Could the container allow for a uid/gid to be passed via an environment variable?

Alternatively, choosing a higher static uid/gid would make it less likely to conflict with another service or container.

[otto-dev]

Came here to say this. Also, in some cases the UID needs to be predictable for permission management.

[otto-dev]

In the meantime, you can use CONSUL_DISABLE_PERM_MGMT #129 and specify what user the container should run under manually (--user flag)

This workaround means the process is now running as the container's root user, so you are exchanging one concern for another

[isaaccarrington]

I'm going to raise a PR. Relates to hashicorp/consul-k8s#347