Boards - Move fetching of board lists to VueX action
As part of GraphQL Boards refactoring, board lists should be fetched through a VueX action, and the data stored in board VueX store.
Some refactoring of the list
model will be required. The use of models being an uncommon pattern in GitLab, we should consider a refactoring getting rid of the model by replacing it with mixins or util functions.
Edited by Florie Guibert