feat: Models for journal

gemeinsamforschen/src/main/java/unipotsdam/gf/modules/journal/model/Journal.java

+package unipotsdam.gf.modules.journal.model;
+
+import unipotsdam.gf.modules.assessment.controller.StudentIdentifier;
+
+public class Journal {
+
+    StudentIdentifier studentIdentifier;
+    String entry;
+    long timestamp;
+    Visibility visibility;
+    String category; //TODO enum
+
+    public Journal() {}
+
+    public Journal(StudentIdentifier studentIdentifier, String entry, long timestamp, Visibility visibility, String category) {
+        this.studentIdentifier = studentIdentifier;
+        this.entry = entry;
+        this.timestamp = timestamp;
+        this.visibility = visibility;
+        this.category = category;
+    }
+
+    public StudentIdentifier getStudentIdentifier() {
+        return studentIdentifier;
+    }
+
+    public void setStudentIdentifier(StudentIdentifier studentIdentifier) {
+        this.studentIdentifier = studentIdentifier;
+    }
+
+    public String getEntry() {
+        return entry;
+    }
+
+    public void setEntry(String entry) {
+        this.entry = entry;
+    }
+
+    public long getTimestamp() {
+        return timestamp;
+    }
+
+    public void setTimestamp(long timestamp) {
+        this.timestamp = timestamp;
+    }
+
+    public Visibility getVisibility() {
+        return visibility;
+    }
+
+    public void setVisibility(Visibility visibility) {
+        this.visibility = visibility;
+    }
+
+    public String getCategory() {
+        return category;
+    }
+
+    public void setCategory(String category) {
+        this.category = category;
+    }
+
+    @Override
+    public String toString() {
+        return "Journal{" +
+                "studentIdentifier=" + studentIdentifier +
+                ", entry='" + entry + '\'' +
+                ", timestamp=" + timestamp +
+                ", visibility=" + visibility +
+                ", category='" + category + '\'' +
+                '}';
+    }
+}

gemeinsamforschen/src/main/java/unipotsdam/gf/modules/journal/model/Visibility.java

+package unipotsdam.gf.modules.journal.model;
+
+public enum Visibility { All, GROUP, DOZENT, NONE
+}