license export function mergeConfig ( target = { } , source ) { const _source = typeof source === 'string' ? { apiKey : source } : source ; if ( ! _source . apiKey ) { throw new Error ( 'No Apm API Key set' ) ; } for ( let i in _source ) { if ( target . hasOwnProperty ( i ) ) { target [ i ] = _source [ i ] ; } } return target ; }