add wait-for-it to backend image

[stephen-w-pracy]

Description

Please, provide here a short description.
Consider including things like:

• An overview of why the work is taking place (with any relevant links); don’t assume familiarity with the history.
• Major changes made and a high-level idea of the chosen approach.
• All the compromises made (in performance, readability, maintainability etc.)
  to achieve the expected result if any

Checklist

Before you move on, make sure that:

• No unintended changes are included
• Spelling is correct
• There are tests covering new/changed functionality
• Commits have meaningful names and changes. CR remarks-like commits are squashed.
• Proper labels assigned. Use WIP label to indicate that state

[stanleegoodspeed]

works locally