Please write a code sample that meets the following business requirements and:

• Solution modeled in the Domain Driven Design convention
• PHP version 8.*
• Framework-agnostic
• The whole thing has been tested with unit tests

Recruitment task:

• Assumptions:
  • The following exchange rates exist:
    • EUR -> GBP 1.5678
    • GBP -> EUR 1.5432
  • The customer is charged a fee of 1% of the amount:
    • Paid to the customer in the event of a sale
    • Collected from the customer in case of purchase
• Cases:
  • Customer sells 100 EUR for GBP
  • Customer buys 100 GBP for EUR
  • Customer sells 100 GBP for EUR
  • Customer buys 100 EUR for GBP

Feedback from employer: the team found the solution to be correct, but it seems too simple

Well. Simple solution is not good, because it is too easy to maintain and understand - interesting approach to long term development process.