Improve doc on sensitive data stored into labels/tags

docs/content/routing/providers/consul-catalog.md

@@ -12,6 +12,14 @@ A Story of Tags, Services & Instances
 
 Attach tags to your services and let Traefik do the rest!
 
+One of the best feature of Traefik is to delegate the routing configuration to the application level.
+With Consul Catalog, Traefik can leverage tags attached to a service to generate routing rules.
+
+!!! warning "Tags & sensitive data"
+
+    We recommend to *not* use tags to store sensitive data (certificates, credentials, etc).
+    Instead, we recommend to store sensitive data in a safer storage (secrets, file, etc).
+
 ## Routing Configuration
 
 !!! info "tags"

docs/content/routing/providers/docker.md

@@ -12,6 +12,14 @@ A Story of Labels & Containers
 
 Attach labels to your containers and let Traefik do the rest!
 
+One of the best feature of Traefik is to delegate the routing configuration to the application level.
+With Docker, Traefik can leverage labels attached to a container to generate routing rules.
+
+!!! warning "Labels & sensitive data"
+
+    We recommend to *not* use labels to store sensitive data (certificates, credentials, etc).
+    Instead, we recommend to store sensitive data in a safer storage (secrets, file, etc).
+
 ## Configuration Examples
 
 ??? example "Configuring Docker & Deploying / Exposing Services"

docs/content/routing/providers/ecs.md

@@ -10,6 +10,14 @@ A Story of Labels & Elastic Containers
 
 Attach labels to your containers and let Traefik do the rest!
 
+One of the best feature of Traefik is to delegate the routing configuration to the application level.
+With ECS, Traefik can leverage labels attached to a container to generate routing rules.
+
+!!! warning "Labels & sensitive data"
+
+    We recommend to *not* use labels to store sensitive data (certificates, credentials, etc).
+    Instead, we recommend to store sensitive data in a safer storage (secrets, file, etc).
+
 ## Routing Configuration
 
 !!! info "labels"

docs/content/routing/providers/nomad.md

@@ -12,6 +12,14 @@ A story of Tags, Services & Nomads
 
 Attach tags to your Nomad services and let Traefik do the rest!
 
+One of the best feature of Traefik is to delegate the routing configuration to the application level.
+With Nomad, Traefik can leverage tags attached to a service to generate routing rules.
+
+!!! warning "Tags & sensitive data"
+
+    We recommend to *not* use tags to store sensitive data (certificates, credentials, etc).
+    Instead, we recommend to store sensitive data in a safer storage (secrets, file, etc).
+
 ## Routing Configuration
 
 !!! info "tags"

docs/content/routing/providers/rancher.md

@@ -12,6 +12,14 @@ A Story of Labels, Services & Containers
 
 Attach labels to your services and let Traefik do the rest!
 
+One of the best feature of Traefik is to delegate the routing configuration to the application level.
+With Rancher, Traefik can leverage labels attached to a service to generate routing rules.
+
+!!! warning "Labels & sensitive data"
+
+    We recommend to *not* use labels to store sensitive data (certificates, credentials, etc).
+    Instead, we recommend to store sensitive data in a safer storage (secrets, file, etc).
+
 !!! important "This provider is specific to Rancher 1.x."
     
     Rancher 2.x requires Kubernetes and does not have a metadata endpoint of its own for Traefik to query.