[Enhancement] Ability to select summary or operationId as category label

[sserrata]

Is your feature request related to a problem?

Today the category label is selected conditionally, based on the existence of the endpoint summary and operationId, respectively.

Describe the solution you'd like

Add a plugin option to allow users to specify whether to use the summary or operationId as the sidebar category label.

Describe alternatives you've considered

n/a

Additional context

n/a