Support Consul KV Enterprise namespaces

Co-authored-by: Romain <rtribotte@users.noreply.github.com>

docs/content/reference/static-configuration/env-ref.md

@@ -426,6 +426,9 @@ Use stale consistency for catalog reads. (Default: ```false```)
 `TRAEFIK_PROVIDERS_CONSUL_ENDPOINTS`:  
 KV store endpoints (Default: ```127.0.0.1:8500```)
 
+`TRAEFIK_PROVIDERS_CONSUL_NAMESPACE`:  
+KV Namespace
+
 `TRAEFIK_PROVIDERS_CONSUL_PASSWORD`:  
 KV Password
 
@@ -534,6 +537,9 @@ Enable Etcd backend with default settings. (Default: ```false```)
 `TRAEFIK_PROVIDERS_ETCD_ENDPOINTS`:  
 KV store endpoints (Default: ```127.0.0.1:2379```)
 
+`TRAEFIK_PROVIDERS_ETCD_NAMESPACE`:  
+KV Namespace
+
 `TRAEFIK_PROVIDERS_ETCD_PASSWORD`:  
 KV Password
 
@@ -789,6 +795,9 @@ Enable Redis backend with default settings. (Default: ```false```)
 `TRAEFIK_PROVIDERS_REDIS_ENDPOINTS`:  
 KV store endpoints (Default: ```127.0.0.1:6379```)
 
+`TRAEFIK_PROVIDERS_REDIS_NAMESPACE`:  
+KV Namespace
+
 `TRAEFIK_PROVIDERS_REDIS_PASSWORD`:  
 KV Password
 
@@ -825,6 +834,9 @@ Enable ZooKeeper backend with default settings. (Default: ```false```)
 `TRAEFIK_PROVIDERS_ZOOKEEPER_ENDPOINTS`:  
 KV store endpoints (Default: ```127.0.0.1:2181```)
 
+`TRAEFIK_PROVIDERS_ZOOKEEPER_NAMESPACE`:  
+KV Namespace
+
 `TRAEFIK_PROVIDERS_ZOOKEEPER_PASSWORD`:  
 KV Password