feathersjs/authentication-popups

@function authentication-popups.authAgent.static.once once
@parent authentication-popups.authAgent.static
@signature `authAgent.once(eventName, handler)` 

Adds an event listener to the `authAgent` whose handler runs only once when the event with given `eventName` is triggered.
1. **eventName** `{String}`: The name of the event to subscribe to.
2. **handler** `{Function}`: A function to be executed to handle the event.