Investigate possible `Payment` domain model

[sokimaaa]

Context

• There is no model for Payment Service.
• Need to take into account multiple aspects of what model is needed for kick-off.
• Discuss with the team to take into account their perspectives.
• Need to consider the possibility of extending the current model in the future, for example by extending to OrderV02.
• Payment Service is going to operate our currency
• The system needs at least representations of own currency (wallet, card and et cetera), user balance, payment progress, payment (or transaction) history, payment (or transactions) with amount, order-related, user-payer.

Acceptance Criteria

• The created V01 model for Payment Service where took into account the requirements.
• JavaDoc presence
• Considered future extending of the model (Generics, method overloading/overriding, deprecation strategy)
• Fully compliant with other models
• Updated to V02 other models that need user info
• Style consistent with other models

Technical Details

• Explore the E-commerce business perspective
• Explore ways to extend the model interface, e.g. Generics, method overloading, overriding, deprecation strategy