add dto, refactor names, update controllers

src/main/java/com/faf223/expensetrackerfaf/dto/IncomeDTO.java

@@ -0,0 +1,18 @@
+package com.faf223.expensetrackerfaf.dto;
+
+import com.faf223.expensetrackerfaf.model.IncomeCategory;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+
+import java.math.BigDecimal;
+import java.time.LocalDate;
+
+@Data
+@AllArgsConstructor
+public class IncomeDTO {
+    private long incomeId;
+    private UserDTO userDTO;
+    private IncomeCategory category;
+    private LocalDate date;
+    private BigDecimal amount;
+}