fix: Added support for update section in DoTransitionWithPayload struct

[CondensedTea]

Description

In this commit I've added Update field to CreateTransitionPayload, with this featrue it is now possible to perform transition with posting a comment

It is backward compatible

Related issue:
#248 -- author of issue decided to use self-made struct I've added in this PR

Jira API docs: link

Tested on Jira v8.5.9 (on-premise)

Example:

var comment = "Closed due to age"

i := CreateTransitionPayload{
		Updates: TransitionPayloadUpdate{
			Comment: []TransitionPayloadComment{
				{
					Add: TransitionPayloadCommentBody{Body: comment},
				},
			},
		},
		Transition: jira.TransitionPayload{
			ID: "171",
		},
		Fields: jira.TransitionPayloadFields{
			Resolution: &jira.Resolution{
				ID: "10101",
			},
		},
	}
	resp, _ := jiraClient.Issue.DoTransitionWithPayload(task.ID, issue)

Checklist

• Unit or Integration tests added
  • Good Path
  • Error Path
• Commits follow conventions described here:
  • Conventional Commits 1.0.0
  • The seven rules of a great Git commit message
• Commits are squashed such that
  • There is 1 commit per isolated change
• I've not made extraneous commits/changes that are unrelated to my change.

[benjivesterby]

Please update the new fields to include omitempty in their struct tags

[CondensedTea]

Please update the new fields to include omitempty in their struct tags

Thanks for pointing this out, fixed