[Chore] Tests enhancements

[DenuxPlays]

Instead of having multiple helper method we should have an Tester struct with an TesterBuilder.
Also once loco supports multiple tests we should be able to start opensearch instances when needed using testcontainers.

ToDos:

• Refactor test setup from using functions to a Tester that initializes everything (returning AppContext or accepting test request)
• Able the mock apis like GoCardless
• add switch to start individual Opensearch instance where needed
  • only where needed because it uses a lot of ram and needs time to start up
• use multithreaded tests when loco support its
  • async tests loco-rs/loco#1237
  • test: Use diffrent ports for tests loco-rs/loco#1093