add notes for edit+retry

servicepulse/intro-editing-messages.md

@@ -0,0 +1,19 @@
+---
+title:  Editing failed messages
+summary: Describes the concept of editing and retrying messages in ServicePulse
+component: ServicePulse
+reviewed: 2019-07-04
+---
+If a message cannot be successfully retried it is possible to modify that message prior to retrying it.
+
+
+Enabling
+- talk about the config? Say you must contact us?
+
+Editable content
+- headers on all messages
+- locked headers
+- message bodies json/xml
+
+Limitations
+- The original failed message must be available when the edit+retry is processed