Pertentangan asas kebebasan berkontrak dan keseimbangan para pihak dalam suatu perjanjian : studi kasus perkara antara PT. Sapta Sarana Persona Prima dan Conoco Philips [Gulf Resources] = Contention freedom principle contract and balance parties in an agreement : case study controversy between PT. Sapta Sarana Persona Prima and Conoco Philips [Gulf Resources]