5925 test mail connection

[lache-melvin]

Fixes #5925

👩🏻‍💻 What does this PR do?

Adds mail test connection step to test_connection tool

💌 Any notes for the reviewer?

🧪 Testing

• With no mail settings in local.yaml - passes with message saying "only required on central"
• With mail settings present - errors - could not get connection
• Start mailhog and re-run - succeeds

📃 Documentation

• Part of an epic: documentation will be completed for the feature as a whole
• No documentation required: no user facing changes or a bug fix which isn't a change in behaviour
• These areas should be updated or checked:
  1.
  2.

[mark-prins]

🚢 love it!
a :nit re the docs - tested and working nicely though 🙏

[lache-melvin]

Adding the step was very nice and easy to write! Thanks for the effort on the tool, cleaning up the steps 🔥