Adds proxy cache limitation (#1374)

Co-authored-by: Steven Smith <[email protected]>

Author: stevsmit

modules/proxy-cache-limitations.adoc

@@ -5,4 +5,6 @@ Proxy caching with {productname} has the following limitations:
 
 * Your proxy cache must have a size limit of greater than, or equal to, the image you want to cache. For example, if your proxy cache organization has a maximum size of 500 MB, and the image a user wants to pull is 700 MB, the image will be cached and will overflow beyond the configured limit.
 
-* Cached images must have the same properties that images on a Quay repository must have.
+* Cached images must have the same properties that images on a Quay repository must have.
+
+* Anonymous users cannot pull images through a proxy cache if the image has not been previously cached. This operation requires the creation of a new repository within the proxy organization to store the cached image, and anonymous users do not have the necessary permissions to create repositories.

modules/proxy-cache-procedure.adoc

@@ -23,9 +23,9 @@ The following procedure describes how you can use {productname} to proxy a remot
 By adding a namespace to the *Remote Registry*, for example, `quay.io/<namespace>`, users in your organization will only be able to proxy from that namespace.
 ====
 
-. Optional. In the *Remote Registry username* box, enter the username for authenticating into the remote registry specified in the previous step. For anonymous pulls from the upstream, you can leave this empty. If you do note set a username at the time of creation, you cannot add one without removing the proxy cache and creating a new registry.
+. Optional. In the Remote Registry username box, enter the username for authenticating into the remote registry specified in the previous step. If you leave this empty, Quay will attempt to pull content anonymously from the upstream registry.
 
-. Optional. In the *Remote registry password* box, enter the password for authenticating into the remote registry. For anonymous pulls from the upstream, you can leave this empty. If you do note set a username at the time of creation, you cannot add one without removing the proxy cache and creating a new registry.
+. Optional. In the Remote registry password box, enter the password for authenticating into the remote registry. If you leave this empty, Quay will attempt to pull content anonymously from the upstream registry.
 
 . Optional. Set a time in the *Expiration* field.
 +