Allow multiple projects per issue and pull requests (#36784)

Add ability to add and remove multiple projects per issue
and pull request.

Resolve #12974

---------

Signed-off-by: Icy Avocado <avocado@ovacoda.com>
Co-authored-by: Tyrone Yeh <siryeh@gmail.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: OpenCode (gpt-5.2-codex) <opencode@openai.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>

services/forms/repo_form.go

@@ -412,12 +412,10 @@ func (f *NewPackagistHookForm) Validate(req *http.Request, errs binding.Errors)
 // CreateIssueForm form for creating issue
 type CreateIssueForm struct {
 	Title               string `binding:"Required;MaxSize(255)"`
-	LabelIDs            string `form:"label_ids"`
 	AssigneeIDs         string `form:"assignee_ids"`
 	ReviewerIDs         string `form:"reviewer_ids"`
 	Ref                 string `form:"ref"`
 	MilestoneID         int64
-	ProjectID           int64
 	Content             string
 	Files               []string
 	AllowMaintainerEdit bool