Fix create issue with scope

Fix adding milestone from board scope when creating a new issue on board

app/assets/javascripts/boards/boards_util.js

@@ -107,8 +107,8 @@ export function formatIssueInput(issueInput, boardConfig) {
   const { labels, assigneeId, milestoneId } = boardConfig;
 
   return {
-    milestoneId: milestoneId ? fullMilestoneId(milestoneId) : null,
     ...issueInput,
+    milestoneId: milestoneId ? fullMilestoneId(milestoneId) : null,
     labelIds: [...labelIds, ...(labels?.map((l) => fullLabelId(l)) || [])],
     assigneeIds: [...assigneeIds, ...(assigneeId ? [fullUserId(assigneeId)] : [])],
   };

spec/frontend/boards/boards_util_spec.js

-import { filterVariables } from '~/boards/boards_util';
+import { formatIssueInput, filterVariables } from '~/boards/boards_util';
+
+describe('formatIssueInput', () => {
+  it('correctly merges boardConfig into the issue', () => {
+    const boardConfig = {
+      labels: [
+        {
+          type: 'GroupLabel',
+          id: 44,
+        },
+      ],
+      assigneeId: '55',
+      milestoneId: 66,
+      weight: 1,
+    };
+
+    const issueInput = {
+      labelIds: ['gid://gitlab/GroupLabel/5'],
+      projectPath: 'gitlab-org/gitlab-test',
+      id: 'gid://gitlab/Issue/11',
+    };
+
+    const result = formatIssueInput(issueInput, boardConfig);
+    expect(result).toEqual({
+      projectPath: 'gitlab-org/gitlab-test',
+      id: 'gid://gitlab/Issue/11',
+      labelIds: ['gid://gitlab/GroupLabel/5', 'gid://gitlab/GroupLabel/44'],
+      assigneeIds: ['gid://gitlab/User/55'],
+      milestoneId: 'gid://gitlab/Milestone/66',
+    });
+  });
+});
 
 describe('filterVariables', () => {
   it.each([