Add Swagger documentation

* Split PaymentDTO and PaymentRequest
 * Updated Converters accordingly
 * Use LocalDateTime instead of Date

pom.xml

@@ -16,6 +16,7 @@
     <properties>
         <java.version>17</java.version>
         <modelmapper.version>3.1.1</modelmapper.version>
+        <springdoc-openapi.version>2.1.0</springdoc-openapi.version>
     </properties>
     <dependencies>
         <dependency>
@@ -39,6 +40,11 @@
             <artifactId>modelmapper</artifactId>
             <version>${modelmapper.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.springdoc</groupId>
+            <artifactId>springdoc-openapi-starter-webmvc-ui</artifactId>
+            <version>${springdoc-openapi.version}</version>
+        </dependency>
 
         <dependency>
             <groupId>org.springframework.boot</groupId>