An auth token is required if ACLs are enabled

Link to the Sentinel docs from the guide

Allow users to escape error pages with the back button

Don't panic on unexpeced Consul response

UI command documentation

Prefix Search ACL enforcement

Fixes #3326

Use Vault default grace

Authenticated client volumes

funcs are in the _oss file to ease creating Enterprise versions which
support Quotas and Namespaces.

This commit:

* Fixes the error checking in migration tests now that we are using the
canonical ErrPermissionDenied error
* Guard against NPE when looking up objects to generate the migration
token
* Handle an additional case in ShouldMigrate()

change creation of a migrate token to be for a previous allocation

System ACL enforcement

Status.Members ACL enforcement

Mention network connectivity in federation guide