OZG-7350 add not null validation to type of Fachstelle

collaboration-manager-server/src/main/java/de/ozgcloud/collaboration/fachstelle/Fachstelle.java

 package de.ozgcloud.collaboration.fachstelle;
 
 import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
 
 import lombok.Builder;
 import lombok.EqualsAndHashCode;
@@ -19,6 +20,7 @@ public class Fachstelle {
 	private String technicalId;
 	@NotBlank
 	private String subjectId;
+	@NotNull
 	private FachstelleType type;
 
 	public enum FachstelleType {

collaboration-manager-server/src/test/java/de/ozgcloud/collaboration/CollaborationServiceITCase.java

@@ -94,6 +94,16 @@ class CollaborationServiceITCase {
 			assertThrows(ConstraintViolationException.class, () -> service.createCollaborationRequest(request));
 		}
 
+		@DisplayName("should validate type of zustaendigeStelle")
+		@Test
+		void shouldValidateCollaborationZustaendigeStelleType() {
+			var request = CollaborationRequestTestFactory.createBuilder()
+					.zustaendigeStelle(FachstelleTestFactory.createBuilder().type(null).build())
+					.build();
+
+			assertThrows(ConstraintViolationException.class, () -> service.createCollaborationRequest(request));
+		}
+
 		@DisplayName("should validate zustaendigeStelle")
 		@Test
 		void shouldValidateCollaborationZustaendigeStelle() {