Implement scrollable warning messages in alert boxes (#10700)

* Set warning message content within a TextArea object to enable scrolling within the alertbox.

* Modified getErrorMessage() to utilize a newline delimiter for the join function, displaying its contents on separate lines.

* Updated order of import to comply with checkstyle.

src/main/java/org/jabref/gui/JabRefDialogService.java

@@ -25,6 +25,7 @@
 import javafx.scene.control.ChoiceDialog;
 import javafx.scene.control.DialogPane;
 import javafx.scene.control.Label;
+import javafx.scene.control.TextArea;
 import javafx.scene.control.TextInputDialog;
 import javafx.scene.layout.HBox;
 import javafx.scene.layout.Region;
@@ -79,8 +80,12 @@ public JabRefDialogService(Window mainWindow) {
     private FXDialog createDialog(AlertType type, String title, String content) {
         FXDialog alert = new FXDialog(type, title, true);
         alert.setHeaderText(null);
-        alert.setContentText(content);
         alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
+        alert.setResizable(true);
+
+        TextArea area = new TextArea(content);
+
+        alert.getDialogPane().setContent(area);
         alert.initOwner(mainWindow);
         return alert;
     }

src/main/java/org/jabref/logic/importer/ParserResult.java

@@ -132,7 +132,7 @@ public void setInvalid(boolean invalid) {
     }
 
     public String getErrorMessage() {
-        return String.join(" ", warnings());
+        return String.join("\n", warnings());
     }
 
     public BibDatabaseContext getDatabaseContext() {