Edit & Retry - docs clarifications

[bartekwasielak]

What needs to be addressed:

• How Edit & Retry works (points)
• Emphasize that the 'retried' message has a different ID
• No ServiceControl events
• failing silently (?)
  • this will be addressed soon by Not informing ServicePulse users about “Edit & retry” failure ServiceControl#5122
• situations when Edit & Retry is discarded (logs a warning, but doesn't communicate the reason to the ServicePulse user - to be checked if already covered)
  • this can occur when
    • the message editing feature is disabled (so the action has not been initiated through the user interface) - safe to ignore
    • the original failed message cannot be loaded - safe to ignore
    • locked headers are changed (not possible through UI) - safe to ignore
    • the message body is empty (not possible through UI) - safe to ignore

[SzymonPobiega]

I proposed some minor changes and links to existing docs