infinity money bug :D

This is here to show a small miss with big problems.

- add missing test to
  - TransactionEndpoints
  - TransactionControllerTest
- update Transfer with validation for sender receiver
- add SenderReceiverValidator
- add SenderReceiver

src/test/kotlin/ltd/lulz/controller/TransactionControllerTest.kt

@@ -215,6 +215,24 @@ class TransactionControllerTest {
         result.expectStatus().isCreated
     }
 
+    @Test
+    fun `transfer fail same accounts`() {
+        // given
+        val request = Transfer.Request(uuid, uuid, amount)
+
+        every { transactionService.transfer(any(), any(), any()) } returns Mono.empty()
+
+        // when
+        val result = webTestClient.post()
+            .uri("/transfer")
+            .contentType(APPLICATION_JSON)
+            .bodyValue(request)
+            .exchange()
+
+        // then
+        result.expectStatus().isBadRequest
+    }
+
     @Test
     fun `transfer fail amount to small`() {
         // given