content-repo: add authentication to GET requests

This is to make clients authenticate their media requests even though
the spec doesn't require it yet.

data/api/client-server/content-repo.yaml

@@ -286,6 +286,8 @@ paths:
     get:
       summary: Download content from the content repository.
       operationId: getContent
+      security:
+        - accessToken: []
       parameters:
         - in: path
           name: serverName
@@ -414,6 +416,8 @@ paths:
         the previous endpoint) but replace the target file name with the one
         provided by the caller.
       operationId: getContentOverrideName
+      security:
+        - accessToken: []
       parameters:
         - in: path
           name: serverName
@@ -550,6 +554,8 @@ paths:
         Download a thumbnail of content from the content repository.
         See the [Thumbnails](/client-server-api/#thumbnails) section for more information.
       operationId: getContentThumbnail
+      security:
+        - accessToken: []
       parameters:
         - in: path
           name: serverName