Get project issue type hierarchy

Get the issue type hierarchy for a next-gen project.

The issue type hierarchy for a project consists of:

• Epic at level 1 (optional).
• One or more issue types at level 0 such as Story, Task, or Bug. Where the issue type Epic is defined, these issue types are used to break down the content of an epic.
• Subtask at level -1 (optional). This issue type enables level 0 issue types to be broken down into components. Issues based on a level -1 issue type must have a parent issue.

Permissions required: Browse projects project permission for the project.