Upgrade opengeoweb from 9.15.0 to 9.16.0 and add wmts background map

Needs to be present in MR

• Test script (description of what reviewer should test with checkboxes)
• Which task(s) the MR closes (e.g. Closes #issueID)
• Assignee
• Reviewers
• Milestone
• Release notes

Description

To test

• See that open street map is available under background maps

Issues to check

• #993 (closed)
• #877 (closed)

Closes #993 (closed) #877 (closed) (Should be the same as "Issues to check")