added ComboBox for assigning courses of study to specific student

src/main/java/de/thdeg/grademanager/gui/StudentDetailsController.java

 package de.thdeg.grademanager.gui;
 
+import de.thdeg.grademanager.model.CoursesOfStudy;
+import de.thdeg.grademanager.model.Student;
 import javafx.event.ActionEvent;
 import javafx.fxml.FXML;
+import javafx.scene.control.ComboBox;
 
 import java.io.IOException;
 
+import static de.thdeg.grademanager.gui.MainController.coursesOfStudyList;
+import static de.thdeg.grademanager.gui.MainController.studentList;
+
 public class StudentDetailsController {
 
+    @FXML
+    protected ComboBox<CoursesOfStudy> coursesOfStudyComboBox;
 
+    @FXML
+    protected void initialize() {
+        coursesOfStudyComboBox.setItems(coursesOfStudyList);
+    }
 
+    @FXML
+    protected void assignCoursesOfStudy(ActionEvent event) throws IOException {
 
+    }
 
     @FXML
     protected void switchToMain(ActionEvent event) throws IOException {

src/main/resources/de/thdeg/grademanager/gui/student-details.fxml

@@ -3,6 +3,7 @@
 <?import javafx.geometry.Insets?>
 <?import javafx.scene.control.Button?>
 <?import javafx.scene.control.ButtonBar?>
+<?import javafx.scene.control.ComboBox?>
 <?import javafx.scene.control.Label?>
 <?import javafx.scene.control.TextField?>
 <?import javafx.scene.layout.BorderPane?>
@@ -12,7 +13,7 @@
 <?import javafx.scene.text.Font?>
 <?import javafx.scene.text.Text?>
 
-<BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/18" xmlns:fx="http://javafx.com/fxml/1" fx:controller="de.thdeg.grademanager.gui.StudentDetailsController">
+<BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="500.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/18" xmlns:fx="http://javafx.com/fxml/1" fx:controller="de.thdeg.grademanager.gui.StudentDetailsController">
    <top>
       <VBox fillWidth="false" prefHeight="46.0" prefWidth="600.0" BorderPane.alignment="CENTER">
          <children>
@@ -184,7 +185,7 @@
          <children>
             <HBox alignment="CENTER" prefHeight="52.0" prefWidth="600.0">
                <children>
-                  <Button mnemonicParsing="false" prefHeight="26.0" prefWidth="142.0" text="Studiengang zuweisen" />
+                  <ComboBox fx:id="coursesOfStudyComboBox" onAction="#assignCoursesOfStudy" prefHeight="30.0" prefWidth="189.0" promptText="Studiengang zuweisen" />
                   <Region prefHeight="52.0" prefWidth="42.0" />
                   <Button layoutX="263.0" layoutY="16.0" mnemonicParsing="false" prefHeight="26.0" prefWidth="153.0" text="Kurse + Noten zuweisen" />
                   <Region layoutX="194.0" layoutY="10.0" prefHeight="52.0" prefWidth="46.0" />