Do not add duplicate supervisors in Daisy (#26)

Daisy's API does not support the function "change supervisor" and only what comes down to SQL INSERT and DELETE on a specific table. If the removal of the previous supervisor(s) failed the new one was still added. This change makes it so that if the removal of any (there is no limit in the API) current supervisor fails it will not attempt to add the new supervisor.

Fixes #39

## How to test
1. Configure the Daisy integration in SciPro
2. Enable it (Maven profile)
3. The only currently known way to make removing a supervisor fail is to use a project where they've sent the thesis to the examiner
4. Find one such project in the test server for Daisy (or send one for examination from SciPro)
5. Change the supervisor of the project in SciPro
6. Run the job "Export projects to daisy" (System / Maintenance)
7. See that it logs the failure and that no duplicate supervisors were added to Daisy

Reviewed-on: #26
Reviewed-by: Tom Zhao <tom.zhao@dsv.su.se>
Co-authored-by: Andreas Svanberg <andreass@dsv.su.se>
Co-committed-by: Andreas Svanberg <andreass@dsv.su.se>

core/src/main/java/se/su/dsv/scipro/daisyExternal/http/DaisyAPI.java

@@ -30,7 +30,7 @@ public interface DaisyAPI {
 
     Response addContributor(Integer projectId, ProjectParticipant contributor);
 
-    void deleteThesisPerson(Integer projectId, Integer personId);
+    Response deleteThesisPerson(Integer projectId, Integer personId);
 
     Response createProject(ThesisToBeCreated project);
 

core/src/main/java/se/su/dsv/scipro/daisyExternal/http/DaisyAPIImpl.java

@@ -157,8 +157,8 @@ public class DaisyAPIImpl implements DaisyAPI {
     }
 
     @Override
-    public void deleteThesisPerson(Integer projectId, Integer personId) {
-        thesis()
+    public Response deleteThesisPerson(Integer projectId, Integer personId) {
+        return thesis()
                 .path(String.valueOf(projectId))
                 .path(PERSON)
                 .path(String.valueOf(personId))

daisy-integration/src/main/java/se/su/dsv/scipro/integration/daisy/workers/ProjectExporter.java

@@ -23,6 +23,7 @@ import se.su.dsv.scipro.workerthreads.AbstractWorker;
 
 import jakarta.inject.Inject;
 import jakarta.inject.Named;
+import jakarta.ws.rs.core.Response;
 import java.time.Instant;
 import java.time.Period;
 import java.util.Calendar;
@@ -240,18 +241,31 @@ public class ProjectExporter extends AbstractWorker {
     }
 
     private void updateHeadSupervisor(Project project) throws ExternalExportException {
-        boolean add = true;
+        boolean toAdd = true;
         Set<ProjectParticipant> contributors = daisyAPI.getContributors(project.getIdentifier());
         for (ProjectParticipant contributor : contributors) {
             if (contributor.getRole() == Role.SUPERVISOR) {
                 if (contributor.getPerson().getId().equals(project.getHeadSupervisor().getIdentifier())) {
-                    add = false;
+                    toAdd = false;
                 } else {
-                    daisyAPI.deleteThesisPerson(project.getIdentifier(), contributor.getPerson().getId());
+                    Response response = daisyAPI.deleteThesisPerson(project.getIdentifier(), contributor.getPerson().getId());
+                    if (response.getStatusInfo().getFamily() != Response.Status.Family.SUCCESSFUL) {
+                        LOG.warn("Failed to delete supervisor from project: {} (id: {} / {})",
+                                project.getTitle(),
+                                project.getId(),
+                                project.getIdentifier());
+
+                        // Card 3413
+                        // Do not attempt to add the new supervisor if the old one is still there to prevent
+                        // the project from having multiple supervisors.
+                        // Hopefully Daisy API will soon have support for the function "change supervisor"
+                        // rather than just INSERT and DELETE rows in a table.
+                        toAdd = false;
+                    }
                 }
             }
         }
-        if (add) {
+        if (toAdd) {
             externalExporter.addContributorToProject(project, project.getHeadSupervisor(), Role.SUPERVISOR);
         }
     }