feat: Add Names support on Issue struct

[bored-engineer]

PR Description

Adds support for the expand=names field on the Issue struct. Ex:

{
   "id": "1234",
   "names": {
       "customfield_56789": "Sprint",
       "reporter": "Reporter"
    }
}

From JIRA API: Issues -> Get Issue:

Use expand to include additional information about the issues in the response. This parameter accepts a comma-separated list. Expand options include:

• names Returns the display name of each field.

Checklist

• Tests added
  • Good Path
  • Error Path
• Commits follow conventions described here:
  • https://conventionalcommits.org/en/v1.0.0-beta.4/#summary
  • https://chris.beams.io/posts/git-commit/#seven-rules
• 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.

[bored-engineer]

I didn't add an error path test as I'm not sure there's a relevant one unless you want me to check for nil when the expand option is not specified.

[andygrunwald]

Thanks a lot @bored-engineer