Invoke-JiraIssueTransition hammers Jira Field API

[hmmwhatsthisdo]

Description

Invoke-JiraIssueTransition calls Get-JiraField once per entry in the -Fields parameter, causing unnecessary API traffic and long wait times to transition an issue.

This issue scales linearly (or quadratically in total) with:

• Count of Jira custom fields (correlates to Get-JiraField response size)
• Key-count of -Fields parameter

Related to #515.

Steps To Reproduce

1. Create a Jira instance with a large quantity of custom fields (500+)
2. Attach JiraPS to the instance
3. Create an issue, either via JiraPS or the Jira web UI
4. Transition the issue via Invoke-JiraIssueTransition with some quantity of fields to set in -Fields
5. Observe long call time

Expected behavior

Invoke-JiraIssueTransition finishes quickly (roughly on-par with web UI)

Screenshots

Your Environment

Get-Module JiraPS -ListAvailable | Select Name, Version
$PSVersionTable

JiraPS 2.14.7

Possible Solution

Based on work in #515, it was determined that simply replacing multiple calls to Get-JiraField with the -Name param with a single, unconstrained call (outside of iteration over -Fields) provided significant performance improvements.

While New-JiraIssue and Set-JiraIssue have the benefit of the CreateMeta and EditMeta endpoints on the Jira API (detailing what fields can and cannot be set), transitions lack a corresponding endpoint. A per-issue transitions API call (/rest/api/2/issue/{key}/transitions) may provide enough highly-contextualized information, but it's unclear if this is comprehensive.