Compare gets the list of GitHub issues updated since the `since` date, gets the list of Jira issues which have GitHub ID custom fields in that list, then matches each one.

CreateIssue generates a Jira issue from the various fields on the given GitHub issue, then sends it to the Jira API.

DidIssueChange tests each of the relevant fields on the provided Jira and GitHub issue and returns whether or not they differ.

GetMissingComponents compares configurated components with the Jira issue components.

UpdateIssue compares each field of a GitHub issue to a Jira issue; if any of them differ, the differing fields of the Jira issue are updated to match the GitHub issue.