Fix addEntities() and addFromCollection() generic parameter

src/main/java/edu/kit/datamanager/ro_crate/Crate.java

@@ -84,7 +84,7 @@ public interface Crate {
 
   void setUntrackedFiles(Collection<File> files);
 
-  void addFromCollection(Collection<AbstractEntity> entities);
+  void addFromCollection(Collection<? extends AbstractEntity> entities);
 
   void addItemFromDataCite(String locationUrl);
 

src/main/java/edu/kit/datamanager/ro_crate/RoCrate.java

@@ -229,7 +229,7 @@ public void deleteUrlFromContext(String key) {
     }
 
     @Override
-    public void addFromCollection(Collection<AbstractEntity> entities) {
+    public void addFromCollection(Collection<? extends AbstractEntity> entities) {
         this.roCratePayload.addEntities(entities);
     }
 

src/main/java/edu/kit/datamanager/ro_crate/payload/CratePayload.java

@@ -30,7 +30,7 @@ public interface CratePayload {
 
   void addEntity(AbstractEntity entity);
 
-  void addEntities(Collection<AbstractEntity> entity);
+  void addEntities(Collection<? extends AbstractEntity> entity);
 
   Set<AbstractEntity> getAllEntities();
 

src/main/java/edu/kit/datamanager/ro_crate/payload/RoCratePayload.java

@@ -77,7 +77,7 @@ public void addEntity(AbstractEntity entity) {
   }
 
   @Override
-  public void addEntities(Collection<AbstractEntity> entities) {
+  public void addEntities(Collection<? extends AbstractEntity> entities) {
     if (entities != null) {
       for (var element : entities) {
         this.addEntity(element);