Issues: add Project filter to issues list and search (#22544)

Currently only a single project like milestone, not multiple like
labels.

Implements #14298

Code by @brechtvl

---------

Co-authored-by: Brecht Van Lommel <brecht@blender.org>

models/issues/issue.go

@@ -1572,6 +1572,7 @@ type IssueStatsOptions struct {
 	RepoID            int64
 	Labels            string
 	MilestoneID       int64
+	ProjectID         int64
 	AssigneeID        int64
 	MentionedID       int64
 	PosterID          int64
@@ -1650,6 +1651,11 @@ func getIssueStatsChunk(opts *IssueStatsOptions, issueIDs []int64) (*IssueStats,
 			sess.And("issue.milestone_id = ?", opts.MilestoneID)
 		}
 
+		if opts.ProjectID > 0 {
+			sess.Join("INNER", "project_issue", "issue.id = project_issue.issue_id").
+				And("project_issue.project_id=?", opts.ProjectID)
+		}
+
 		if opts.AssigneeID > 0 {
 			applyAssigneeCondition(sess, opts.AssigneeID)
 		}