Kanban board : Sidebar toggle button doesn’t have an Accessible label.

Issue Summary

On kanban board page, the button which toggles the sidebar doesn’t have an Accessible label in the source code.

Bug Ref: 726737

Steps to Reproduce

1. Navigate to the Jira dashboard page.
2. Navigate to any project from "Projects" menu in the header section.
3. Navigate to the "Expand sidebar (>>)" button in the left navigation.
4. Inspect the code of the button & observe that there is no accessible label. 

Actual Results

The button "Expand sidebar (>>)" which toggles the sidebar doesn’t have an accessible label in the source code. Although the aria-describedby attribute is provided to the button but it is not sufficient method of accessible label.

Also when screen reader user pull up the list of form control for example in JAWS (ins + F5), it just says "button" in the list.

This makes assistive technology difficult to render the purpose of the button to the users effectively.

Expected Results

The toggle sidebar button should have an accessible label provided in the source code.

Provide aria-label="Expand sidebar" (when sidebar is collapsed) to the toggle button in the source code. The aria-label should be updated to "Collapse sidebar" when the sidebar is expanded.

Screenshot

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available