Add API to get issue/pull comments and events (timeline) (#17403)

* Add API to get issue/pull comments and events (timeline)
Adds an API to get both comments and events in one endpoint with all required data.
Closes go-gitea/gitea#13250

* Fix swagger

* Don't show code comments (use review api instead)

* fmt

* Fix comment

* Time -> TrackedTime

* Use var directly

* Add logger

* Fix lint

* Fix test

* Add comments

* fmt

* [test] get issue directly by ID

* Update test

* Add description for changed refs

* Fix build issues + lint

* Fix build

* Use string enums

* Update swagger

* Support `page` and `limit` params

* fmt + swagger

* Use global slices

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

models/issue_comment.go

@@ -110,6 +110,47 @@ const (
 	CommentTypeChangeIssueRef
 )
 
+var commentStrings = []string{
+	"comment",
+	"reopen",
+	"close",
+	"issue_ref",
+	"commit_ref",
+	"comment_ref",
+	"pull_ref",
+	"label",
+	"milestone",
+	"assignees",
+	"change_title",
+	"delete_branch",
+	"start_tracking",
+	"stop_tracking",
+	"add_time_manual",
+	"cancel_tracking",
+	"added_deadline",
+	"modified_deadline",
+	"removed_deadline",
+	"add_dependency",
+	"remove_dependency",
+	"code",
+	"review",
+	"lock",
+	"unlock",
+	"change_target_branch",
+	"delete_time_manual",
+	"review_request",
+	"merge_pull",
+	"pull_push",
+	"project",
+	"project_board",
+	"dismiss_review",
+	"change_issue_ref",
+}
+
+func (t CommentType) String() string {
+	return commentStrings[t]
+}
+
 // RoleDescriptor defines comment tag type
 type RoleDescriptor int