Exploring Opportunities and Challenges for the Spread, Scale-Up, and Sustainability of mHealth Apps for Self-Management of Patients With Type 2 Diabetes Mellitus in the Netherlands: Citizen Science Approach - Catharina Margaretha van Leersum; Marloes Bults; Egbert Siebrand; Theodorus Johannes Josef Olthuis; Robin Enya Marije Bekhuis; Annemieke Ariënne Johanneke Konijnendijk; Marjolein Elisabeth Maria den Ouden (JMIR Diabetes)