[CONTRACT] Create YieldSourceConnectorInterface and ZKLendConnector

[codebestia]

💡 Create YieldSourceConnectorInterface and EkuboConnector

📝 Description

• The idea behind is to solve the issue of using One yield source. here yield source can but connected to the application as via a connector contract that follows an interface pattern. Each connector must follow a particular pattern and must use the yield source interface. The problem that might be faced is that each connector has to forward the caller to the yield source as the yield source account will be connected to the vault

🔢 Feature

• implement entrypoint to withdraw from yield source
• implement entrypoint to deposit to yield source
• Implement entrypoint to get supported token
• Implement entrypoint to get yield amount
• Implement entrypoint to get APY
• Implement entrypoint to withdraw yield (if applicable)

✅ Acceptance Criteria

• All entrypoint and logic accounted for
• All test passed
• All test for entrypoint accounted for

[codebestia]

Closed with #21