As identified in T378527#10412817, the minimum number of tasks per topic GrowthExperiments maintains is currently defined in community configuration as minimumTasksPerTopic. Since that value is not specified in the SuggestedEditsSchema, it currently cannot be configured by the community. Practically speaking, the value is constant and specified in the codebase (in the form of default values).
To be able to move with T378527: Surfacing structured tasks: Populate Add Link suggestions for more articles, we need to be able to change the minimum number of tasks per topic on per-wiki level. To accomplish that, we need to move minimumTasksPerTopic to PHP configuration.