added credential menu

src/main/java/Vault.java

@@ -120,4 +120,15 @@ public class Vault implements VaultInterface {
             println("Your PWs don´t have numbers anymore.");
         }
     }
+
+    public void credentialMenu() {
+        StringBuilder sbcm = new StringBuilder();
+
+        sbcm.append("Configure credentials:\n");
+        sbcm.append("- add credential: a\n");
+        sbcm.append("- show credential: c\n");
+        sbcm.append("- exit: e\n");
+
+        println(sbcm.toString());
+    }
 }

src/test/java/VaultTest.java

@@ -27,6 +27,14 @@ public class VaultTest {
         vlt.inputS = System.in;
     }
 
+    @Test
+    void openCredentialMenu() {
+        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+        vlt.outputS = outputStream;
+        vlt.credentialMenu();
+        assertTrue(outputStream.toString().startsWith("Configure"));
+    }
+
     @Test
     void addCredentialTest() { vlt.addCredential();}