Assign pull request to project during creation (go-gitea#28227)

When creating a pull request, allow directly assigning it to a project,
as it is already possible for issues.

After:


![grafik](https://github.com/go-gitea/gitea/assets/47871822/01dc2b3d-d56a-4053-b2fc-138725d7633a)

routers/web/repo/compare.go

@@ -844,6 +844,7 @@ func CompareDiff(ctx *context.Context) {
  }
  }
 
+ ctx.Data["IsProjectsEnabled"] = ctx.Repo.CanWrite(unit.TypeProjects)
  ctx.Data["IsAttachmentEnabled"] = setting.Attachment.Enabled
  upload.AddUploadContext(ctx, "comment")
 

routers/web/repo/pull.go

@@ -1371,7 +1371,7 @@ func CompareAndPullRequestPost(ctx *context.Context) {
  return
  }
 
- labelIDs, assigneeIDs, milestoneID, _ := ValidateRepoMetas(ctx, *form, true)
+ labelIDs, assigneeIDs, milestoneID, projectID := ValidateRepoMetas(ctx, *form, true)
  if ctx.Written() {
  return
  }
@@ -1449,6 +1449,17 @@ func CompareAndPullRequestPost(ctx *context.Context) {
  return
  }
 
+ if projectID > 0 {
+ if !ctx.Repo.CanWrite(unit.TypeProjects) {
+ ctx.Error(http.StatusBadRequest, "user hasn't the permission to write to projects")
+ return
+ }
+ if err := issues_model.ChangeProjectAssign(ctx, pullIssue, ctx.Doer, projectID); err != nil {
+ ctx.ServerError("ChangeProjectAssign", err)
+ return
+ }
+ }
+
  log.Trace("Pull request created: %d/%d", repo.ID, pullIssue.ID)
  ctx.JSONRedirect(pullIssue.Link())
 }