Intervention With WhatsApp Messaging to Compare the Effect of Self-Designed Messages and Standardized Messages in Adherence to Antiretroviral Treatment in Young People Living With HIV in a Hospital in Lima, Peru: Protocol for a Nonblinded Randomized Controlled Trial - Jeffrey Freidenson-Bejar; Dianne Espinoza; Rodrigo Calderon-Flores; Fernando Mejia; Elsa González-Lagos (JMIR Research Protocols)